The vast majority of the violence that occurs in the US is perpetrated by drug dealing gangs and against other drug dealing gangs. Tragically, there are innocent victims of this gang violence, but these gangs don't obtain guns legally, so any anti-gun legislation would have little effect on them. Criminals, by definition, don't obey the laws, law abiding citizens do. There are daily examples of law abiding gun owners thwarting crimes, they just are reported upon with as much fervor as the massacres -- which, by the way, are NOT an epidemic, they're just sensationalized for political gain. Lastly, there is no way to account for the number of crimes not committed due to the mere suspicion that the would-be victim is armed. Criminals polled in prison have said repeatedly in studies that ARMED citizens are a much greater deterrent than the police.