99% of the time they kill only each other. Nobody's perfect.
That's it? We're to legalize all drugs nationwide because a few innocents in some major cities are accidentally killed? And how many will die because of legalization? How many additional accidents while on drugs, overdoses, spread of AIDS and other diseases, suicides ...?
Let's have some perspective here.
Of course not ... that's just the worst of it. When criminals collect drug-war-inflated profits, all manner of criminality is financed. Then there's the crime committed by users to pay those drug-war-inflated prices.