exceptions which are confirming the rule
the cases of going postal with white arms are surely fewer and with lesser casualties than the gun-powdered ones.
crimes will still happen no matter what, even with bare hands. but actually having to do your kill from up close requires much more cool blood/insanity than having to kill by just pulling a trigger from a few meters away, and therefore many people which could do it with a gun, won't do it with a knife.