"Even a civilian armed response would have hurt no one but the agressor

So... the logic is: EVERYONE who legally can should carry a gun so they can 'respond'? Sounds like 'stand your ground' ³! When everyone...or even MOST ...are carrying, that means short-tempered trigger-happy George Zimmerman's in every theater, bar, college classroom. This means a LOT more 'threats' will be perceived and weapons drawn...with 'responses' by nice, sane, even-tempered, well-trained guys like olddude! Do you REALLY think you can teach reasonable gun handling and restraint to 30-50-75% of the populace?
I sure hope *I* am not in the crossfire when a theater full of well-intentioned 'armed civilians' perceives a threat.

You CANNOT expect reasonable behavior from a random group!