Yeah, crazy criminals are totally "deterred" by armed citizens, laws, etc... If gun control, laws and cops don't deter these nutjobs, why in God's name would armed citizens deter them?
They are mentally ill and are trying to become an anti-hero.
You don't become an anti-hero by attacking a hard target, you attack a soft target. How many of these nuts attack police stations? Gun stores?
They go after soft targets, gun free zones where they can inflict maximum damage with no resistance. What happens as soon as an armed response confronts them? They usually kill themselves. The Oregon mall shooter is a prime example. They CCW holder didnt even get off a shot but as soon as the gunman saw there was someone else there armed he killed himself.
So yes, they are deterred by force, just not any laws.