I'm pretty much in line with what Phil said. For me it's better to train with the idea of doing the least amount neccessary. I really have no moral or ethical problem with the idea of using violence, even extreme violence if that is what is needed to end the situation. I still think of my tai chi instructor saying that you can end most physical confrontations by staying one step lower in violence than the attacker.
If he is trying to hurt you, stop him.
If he is trying to maim you, you may have to hurt him.
If he is trying to kill you, you may have to maim him.
This fits well with my personal feelings and also with what I'm learning in aikido. We train relatively softly but we are still shown how to "ramp up" the techniques when needed. Our baseline technique usually falls into the area of controlling uke as opposed to throwing or breaking uke. We're going on the idea that it's easier to train with the idea of softness and spike it when needed than to train hard (bad word choice but all I can come up with
) and try to soften it when needed.
Of course this is all theory. I've yet had any situation get past "just words". Who knows, maybe if I'm ever faced with the prospect of having to deliberately injury another person I'll freeze and find I just can't do it...on the other hand I might find I like it