Ever heard it said that you are more likely to be harmed if you carry a knife than if you don't? Something to do with how you're more likely to stand your ground if you are armed, therefore leading to injury to one or both parties. It's proposed that this is the same with killing, that if we are not prepared to kill an attacker then they are less likely to kill us...real or not real?
It is proposed that crime rates should be lowered by making it illegal to kill, even in self-defence.