The issue here is more or less. A kitchen knife is bound to cause less casualty than a machine gun in the hand of a psycho, hence we require licenses for gun. It's not to eliminate death through violence, it's to reduce and deter it. We don't want people to reach for the nearest machine gun whenever they have a domestic quarrel (obviously we don't want people to reach for a knife either, but I hope you get my point) or when their neighbor's dog poops in their yard.