Why does Maxwell's Demon need to be exorcized? There has been quite a lot of fuss over the years to explain why the Demon does not represent a violation of the Second Law of thermodynamics.  Many papers bring information or complexity theory on board, explaining either that the recording or the discarding of information supplies the missing entropy, or else re-defining a new entropy which will in increase despite the Demon's efforts.
Why do all these authors have such a strong expectation that some argument must be found to restore the second law?  Given what I think is a standard understanding of entropy, there is simply no reason to expect this.  
Once an agent's preferred macro-parameters are settled, phase space is divided into chunks and entropy refers to the volumes of these chunks.  A different agent, with access to a differing level of experimental control, would have a differing set of macro-variables and a different partitioning of phase space.  Such an agent could definitely implement what appears to be, on the first agent's partition, a decrease in entropy.  Couldn't they?
 A: The standard version of Maxwell's Demon allows for a perpetual motion machine, producing an infinite amount of work from a finite-temperature reservoir. This seems too good to be true, and since nobody has ever successfully built a perpetual motion machine, it is widely believed that these are unlikely to exist.
A number of physicists believe that Maxwell's Demon has been exorcised. This was done using Landauer's principle:

the minimum possible amount of energy required to erase one bit of information is
  kT ln 2.

In order to operate, the Demon needs to remember which way he sent the molecules. Eventually, his memory becomes full, and he is unable to keep operating. Once he starts erasing his memory, he can no longer reduce the entropy of the system for free.
Viewed in another way, the Demon is simply a heat engine that operates on the difference of temperature between the system and his memory (which has temperature 0).
A: If a physical process could bring about an energy movement from a colder to a hotter body, with no other change, at the macroscopic thermodynamic level, in the rest of the universe (this what Maxwell's thought-experiment purports to do) then it would mean the 2nd law did not hold universally (in the thermodynamic limit where it becomes a precise statement). However, no one has ever succeeded in proposing a physical process which actually achieves this, so as far as we know the Maxwell daemon is a physical impossibility.
It is good practice to invest intellectual effort in this way, I mean to check that a process ruled out by the 2nd law is indeed not possible, because it helps our understanding to know that the 2nd law does indeed hold. This is important because that law, or descriptive principle, plays such a useful role in many areas of science, especially chemistry.
A: 
Why do all these authors have such a strong expectation that some
  argument must be found to restore the second law?

Could it simply be because no one has ever actually observed violations of the second law? Just like no one has ever actually observed speeds exceeding the speed of light?
Hope this helps.
A: Obvious violation of the second law of thermodynamics:
Deionized water in an electric field:
https://youtube.com/watch?time_continue=7&v=17UD1goTFhQ
The turbulent motion is powered by ambient heat (no other source of energy is available) and can convert this heat into work, e.g. by rotating a waterwheel.
