Yah and the Nazis try to stop you freeing the Jews violently and you try to stop them from stopping you violently and... you get the idea.

Well, if you think violence is only justified in self defense a person who killed a police trying to stop him might as well say that he did so because the police was trying to shoot him.

Then are you saying that as long as it was in self defense or in attempt to help the others (like the "great" job the US is doing in Afghanistan combating terrorists whose number increased even more after they came), violence can be justified? But then, if you are a murderer (for the sake of this scenario) and someone shoots you, wouldn't you shoot him back and think your action had been perfectly justified? As long as your argument is valid of course.

Well then, if your baby relative scratches you, you can go accuse her of being "violent".