Why is it thought that normal physics doesn't exist inside the event horizon of a black hole? A black hole is so dense that a sphere around it called the event horizon has a greater escape velocity than the speed of light, making it black. So why do astronomers think that there is anything weird (or lack of anything Inc space) inside the event horizon. Why isn't simple the limit to where light can escape and in the middle of event horizon (which physically isnt a surface) is just a hyper dense ball of the matter that's been sucked in and can't escape just like light. Why is it thought that the laws of physics don't exist in the event horizon?
 A: For large enough black holes, space is still weakly curved at the event horizon, so of course we should expect that normal physics still exists there. An infalling observer wouldn't experience anything out of the ordinary when crossing an event horizon.
What is true is that for an outside observer, it's impossible to probe what's happening inside the event horizon of a black hole. (The best you can do is wait a long time and collect the outgoing Hawking radiation.) So from the point of view of such an observer, you can't really tell the difference between living in a world where spacetime keeps going across the horizon, or living in a world where space just ends there and some radiation emerges. This might be the sort of idea your teacher was getting at. You might want to look up "black hole complementarity" to learn more.
A: If you are inside the event horizon of a spinning black hole, there are closed timelike curves--paths through spacetime which, when you progress them into the future, they end up in their past.  These curves clearly violate the principle of causality, and thus, the region inside the black hole can be considered unphysical in a sense.  
Also, of course, the spacetime singularity also lives inside of the black hole's horizon.  Classically, it is a point or ring of infinite density at which the curvature of spacetime is infinite.  Spacetime histories intersecting the singularity must end if you believe in classical mechanics.  So, there is clearly some new physics there--most relativity researchers believe in something called the Cosmic Censorship conjecture, which says that nearly all* physically reasonable solutions of Einstein's equations hide their black hole singularities behind a horizon.
*There are some known exact solutions where physically reasonable matter distributions collapse to horizonless singularities, but they are believed to form a set of measure zero in the space of matter distributions.  
A: For example, for starters, outside a Schwarzschild black hole horizon, particles can move in any direction, but time only goes one way. i.e. forward.    Inside the horizon, particles can only move inward toward the central singularity, i.e. one way, but time can go either forward or backwards.   This is a result of the "light cones tipping over".    That's different. 
