I'm not sure how to say it...
Say I'm walking in front of a police station, with cops outside having a smoke, and a crackhead runs up to me and starts throwing punches. I'm going to put my arms up to block the punches and let the cops stop him. Now say its the same place, but I'm carrying concealed and a crackhead runs up to me and pulls out a gun. I don't care where I am. He's going to get shot.
If I'm in a bar and a drunk guy starts yelling at me incoherently, I'm going to tell a bouncer. If he breaks a bottle and tries to stab me with it, I'm going to punch him, or try to stab him back, or something like that.
The violence (real or potential) of the situation overrides the possibility of me being arrested. That being said, if the chances of me getting arrested are low to none, I might get MORE violent than I normally would, but I won't get violent just because of that.