Chris Kyle was a decorated Navy SEAL, widely reported to be the most lethal sniper in American history, with about 160 kills to his credit (unofficially). It would be hard to conceive of a man more suited to responding appropriately to the threat of gun violence with reciprocal deadly action - however last weekend Kyle and his friend wound up dead at the shooting range where they were practicing - their own guns close by presumably (they were shot by an Iraq war veteran).
I would ask any reasonable person - if elite-trained firearms experts like Mr. Kyle and his companion were unable to defend themselves from unexpected gun violence - can anyone reasonably be expected to protect themselves simply by arming themselves with a weapon?
Humans are the most dangerous animal and in many cases, if one decides to target you by surprise, having a gun on you is not likely to save you. Better to keep the guns out of the hands of dangerous people and empower law enforcement to do its job rather than put more guns on the street which due to probability will eventually fall into the hands of those dangerous or unstable individuals.