Why is superdeterminism generally regarded as a joke? Before anything, I'm sorry for being an outsider coming to opine about your field. This is almost always a stupid decision, but I do have a good justification for this case. I've been reading about superdeterminism and it bothered me that most of you treat it as a joke. Well, before anything, I think at this point in history we should've already learned the lesson: ridiculous sounding ideas often end up becoming standards science, and that form of idealogical bullying should never exist. But, if at least the arguments were convincing, one could make an excuse for the author. Except not, his arguments sound just like someone with total lack of understanding of idea who rants against it just because he doesn't like it. "Superdeterminism would mean nature is sending magic agents to control our brains and conspire against us!" Is this even serious?
Yes, as a computer scientist I do think superdeterminism is the most natural approach to how the universe works. On my view the idea of "free will" - as in, something coming from outside the universe, interacting with the information stored in our brain and determining what we do physically - is the sketchy approach, not the opposite. I do think true randomness is the one that requires a lot of magical intervention, while superdeterminism is much more solid. And I even think recent insights support it without need for any "magical agents". But that is not the reason I'm mad - after all, I'm an outsider and my views doesn't matter a dime. It is because such an important idea with huge implications is regarded as a joke and not even considered just for matters of taste, with no actual proof or evidence of the case. And this is something I do have the right to complain, regardless of the field.
So, please, could anyone justify this prejudice?
 A: The real issue here is obscured by inane terminology and bad thinking. 
The real issue is, what sort of "locally deterministic theory" could reproduce the experimentally successful predictions of quantum mechanics? Locality here means, not just that causal influences have to pass through space (rather than acting instantly at a distance), but that they don't go faster than light. 
The key discovery of John Bell, immortalized in his theorem, is that there are experiments in which quantum mechanics predicts that there are correlations of a sort which cannot be produced by a locally deterministic theory. 
The basic paradigm is that two particles are produced at a point, and move apart in opposite directions towards two rotatable filters. There are particle detectors on the far side of both filters. The probability that the particle will get through the filter depends on the filter's angle of orientation. The orientation of the filter is set while the particles are in flight, when they are too far apart for a light-speed influence to connect them. Yet whether they get through the filters or not, is highly correlated in a way that can't be produced by a locally deterministic theory with a light-speed limit. For more, see "Bell's theorem". 
Bell's theorem is about probabilities. It is not literally impossible for a locally deterministic physics to reproduce the right results, but it would have to be an endless long-running coincidence, as if cosmic rays kept arriving from the other side of the universe in order to block the particles from getting through with the required frequency. 
The point is that the filter orientations can be set according to any rule, the probabilities of getting through at the different ends are both highly correlated with each other and depend on what the orientations actually are, and the filter orientations can be "chosen" in such a way that no lightspeed causal influence can connect them. So the hypothetical causal influence that determines whether the particles get through, would have to "know" what the orientations were in advance. And since the orientations could be chosen e.g. according to the digits of pi, or the letters of "Moby Dick", or the behaviors of rats in a maze, you would have to suppose that this sequence of information was programmed into the outside causal influence (like the cosmic rays) in advance. 
That is the idea that is "regarded as a joke". But here is where the inane terminology and the bad thinking enter to confuse the issue. 
Bell posed his scenario in terms of experimenters choosing the filter orientations. He said a loophole might exist, if the experimenters' own choices are not free, and he called this "superdeterminism", as if ordinary determinism was just about experiments and not also the people who make them. 
In any case, this offers no improvement in terms of probability. Before, we had cosmic rays with "Moby Dick" pre-programmed into them. Here, we have (presumably) mysterious influences which would prevent experimenters from conducting the "Moby Dick" version of the experiment. It's just as silly, and in any case, Bell-type experiments have now been done many times, so the improbable thing has come to pass. (It would be interesting to have a lower bound on just how improbable the outcomes of all the world's EPR experiments would be by now, assuming local determinism.) 
So, although there actually is a prejudice against determinism among many people brought up on quantum mechanics, and although many people have a philosophical prejudice in favor of free will, neither of those really has anything to do with the issue here. The core issue is the fact that locally deterministic theories can only produce Bell correlations by coincidence, and that has a probability approaching zero as the experiments keep getting repeated and the predictions confirmed. If you want determinism in subquantum physics, you need nonlocality (Bohmian mechanics), causality backwards in time (various "interpretations"), perhaps some form of emergent space (with an underlying causal network that is nonlocal)... 
This paper is a more accurate and scholarly expression, using a contemporary form of causal analysis, of what I am trying to say. When I say it needs cosmic rays pre-programmed with Moby Dick... that's an example of what they call "fine-tuning". The local causal influences responsible for producing nonlocal Bell correlations would have to be tuned in advance to produce the required effects. 
A: 
Why is superdeterminism generally regarded as a joke?

My personal (somewhat facetious) answer to that would be because people lack imagination. I don't think of superdeterminism in terms of conspiracies, but rather retrocausality, and do not find it ridiculous if phrased this way.
Basically, I don't believe there's really something like a physically significant arrow of time - just an arrow of perception of time. Reality doesn't care how we subjectively experience time as somehow flowing from one moment to the next.
Some anecdotal evidence for this: First, relativistic theories are reparametrization-invariant - there isn't really a preferred notion of time. Then, there's the idea due to Stueckelberg and Feynman that anti-particles are basically just particles propagating backwards in time, or the time-symmetric reformulation of electrodynamics. Also, there's the fact that in general relativity, we need to solve for a consistent space-time (which takes future 'boundary conditions' into account), with the aggravation that space-time might possibly have a non-trivial topology at the quantum level.
This is also the basic idea behind the (somewhat naive) transactional interpretation of quantum mechanics.
A: I think you are prejudiced yourself if you say 'I do think superdeterminism is the most natural approach to how the universe works'. This is not meant as criticism, I just want to say that your mind is shaped by the world you perceive, and that world looks deterministic. 
Quantum mechanics and its randomness represent a different view on the (microscopic) world, and it does look unnatural to a mind that is shaped by the behavior of the (macroscopic) world. When I studied physics, it took me years to get some intuitive understanding of the quantum mechanical world, because it contradicted my intuitive understanding of the world of classical physics in so many ways. 
Personally, I am glad about the randomness in quantum mechanics, because to me it seems that it negates determinism and makes free will possible.
A: First of all, "loopholes" is no disrespect. It's standard nomenclature. Given a law, a "loophole" is a way to circumvent it. Bell's inequalities, in their mathematical formulation, are laws that prevent superdeterminism, so if we believe it should exist, we have to find loopholes in the assumptions. It might be that the loophole is so big that the whole law becomes nonsense, but till now, nobody has found one - except the free will.
Except for a few really outspoken critics, I don't think that people regard superdeterminism as a "joke". If you are interested, here is a good summary about what is known by a computer scientist: http://www.scottaaronson.com/democritus/lec18.html
It also tells you that for Bell's inequalities, the concept of "free will" is actually not "murky" but very clear: The detector settings must not be completely predetermined by the history of the universe. You can accept that assumption to be true or not.
In the end, of course, it means you have to decide: Is everything in the universe predetermined, or are there any choices possible that are not fully predetermined by the state of the universe? If the latter exists, you can't have superdeterminism. That's what Bell tells us. So let's assume we have superdeterminism. And then? Nothing. It doesn't give you any new predictions and despite that, it actually tells you that what you are doing is futile anyway, because your experiments don't fulfill the basic requirements we pose about experiments (reproducibility, parameters can be freely set, etc.), so in principle, you could stop right there. Then again, you won't stop, because you're predetermined not to. 
Thus superdeterminism is a stance in philosophy not science in its modern form (and this question is not physics, but philosophy) - and many physicists/mathematicians strongly reject philosophy in science, they just don't get anything out of it. So, physicists don't treat superdeterminism as a joke, it's just not a position they feel comfortable with and since it doesn't predict anything anyway, they can just take a different position or none at all.
A: You say "ridiculous sounding ideas often end up becoming standards science" - but take into account that "ridiculous sounding ideas" much more often, by a large factor, end up becoming no science at all.  
I agree that "that form of idealogical bullying should never exist" - except that it's not ideological, but just a practical matter of deciding which claims to spend time on understanding and possibly verifying.
When you ask scientists for "actual proof or evidence of the case" - it prove, that some new, and fairly unusual theory is invalid, you ask people to do a lot of work - but why should they do this work?
They would be interested to do this work - without even asking them - if someone provides some kind of evidence convinces them that there is a chance the new idea is at least useful enough to spend time on.
That's all. 
I think “Extraordinary claims require extraordinary evidence” (Carl Sagan) applies perfectly to that.
A: Ideas shouldn't be treated as jokes but superdeterminism is false: it is incompatible with the best available theory of knowledge. 
First, a digression on the theory of knowledge. Any instance of adaptive complexity has to be explained. For example, as Paley noted, if you find a watch and notice that its parts fit together in such a way that they accurately tell time and that a small change in the arrangements of the parts would destroy its ability to tell time, then some process must have set it up to do that. The information required to set up such a system is knowledge. Philosophers often think of knowledge as being something a person believes but adaptive complexity in an artefact like a watch or the wing of a bird or whatever all require explanation and the explanation has to be pretty similar in each case because what requires explanation is pretty similar. Namely, whatever set up the system has to have started out without that information and then created it. Since it didn't start out with the knowledge, it can't just magically produce the right answer in a single leap, rather it has to produce variations on its current information and then selected among those variations. There has to be some medium in which the information is stored and can be easily accessed, read and used to produce things like watches or butterfly wings or whatever. In the case of artefacts that humans make, the information can be stored in books, computer programs and so on. In the case of biological evolution, the information is stored in genes. But any such information has to be stored somewhere.
If superdeterminism was true then there would have to be some system that can mess about with the human brain in such a way as to gives people specific ideas. It would not be enough to make random changes because such changes would not produce the idea of making a specific measurement. A random change might produce an epileptic fit or brain damage or the brain might just ignore it depending on the kind of change but it won't produce a specific idea. So where is this system? Where does it store the information required to manipulate human experimenters? How did it create that knowledge without anybody noticing?
And suppose that such a system existed and that it had somehow concealed itself from us. Why would it do that when it could cooperate for mutual benefit? Even if it has a much greater information storage capacity or processing speed or whatever, surely it can figure comparative advantage or at least read about it in economics books? Comparative advantage means you should do what you're best at and leave other people to do stuff you're not so good at. So if it can do numerical integration in fifty dimensions without breaking a sweat and it had a reason to do so it could contract out less urgent stuff to humans.
Finally, I think the problem physicists have with quantum mechanics is largely that they fail to take it seriously as a description of how the world works. For example, quantum mechanics is a local theory and the non-locality is a result of trying to force it into a classical shape, see
http://arxiv.org/abs/quant-ph/9906007
http://arxiv.org/abs/1109.6223
