I agree that limiting your actions in a fight is important for proper defense, but it goes beyond that as well. There can be terrible outcomes when people aren't careful and don't limit the violence of their attacks. You can injure them too much, or you can inspire them to fight too hard, resulting in a greater chance they will injure you.

Unfortunately, when people fight they are often too angry to think well. Other people should try to stop such fights instead of just standing around watching.