In my opinion, the argument that you need armed citizens to stop the bad guys is bullshit. I own quite a few guns, and unless it was life or death and the criminal is aiming his gun at me, I am not randomly shooting into a crowd. Anyone who has ever shot a hand gun can tell you that the accuracy is nowhere near that of a rifle. Shit, I shoot all the time and have a hard time hitting anything small beyond 30-40 feet. Throw in life or death situation and a quick draw, who knows what the fuck you hit.
I have weapons for home protection, fun, hunting, and just in case...the revolution ever comes...
Seriously though, guns are here to stay in the United States and idiots who own them and go on random shooting sprees is just something we will have to deal with, unfortunately.