First, try working in North Philly, or walking home from your girlfriends house at 11 p.m. in Philadelphia and tell me you don't wish you had a firearm on your side for protection. My motto is it's better to have and not need it, rather need it and not have it.
Second, If the gun went off inside the theater then the trigger was pulled. If he was dumb enough to play with the weapon while it was locked and loaded, then he is one of the many people who should not carry a weapon in public. Carrying in public is a responsibilty not just to yourself but everyone around you, it is not for everyone.
Lastly, it's my God given right as an American. I have the right to protect myself and my family, not just in my home, but anywhere.
Hope that helps.