most of the gun crimes in the US are drug related ie. gang vs. gang,
if the little fuckers want to kill each other good for them, less idiots for the cops to shoot.

also since most murders are by drug gangs it is safe to assume that they can get their weapons out of country like they get drugs, so banning guns will only make it harder to defend yourself from some sad gangsta "I-hold-my-gun-sideways-and-can't-hit-shit" types who get their guns from some colombian.