Yea but in all honesty are you going to go into a theatre if some 40 year old guy has a 9mm strapped to his hip and keeps eyeing up all the 20 somethings and giving them dirty I have my eye on you looks.
People with good intentions can be just as insane and could always hit innocent people in the crossfire or be the cause of even more violence.
Even cops can cause this sort of thing, if a banks being robbed and they have no intention of using violence but then the cops surround them, now the cops are putting the hostages in equal danger instead of letting the robbers out with insured money and dealing with them later in a safer enviroment.
It's really a no win, the fact is when thins like the internet cafe vigilante go down, it's just dumb luck no one gets hurt.