You don't want to get punched, then don't push a cop. He probably could have handled the situation better, but I do not fault him. She was trying to help a friend resist arrest. You just don't do that and not expect consequences.
You have the right to subdue/neutralize the target by using the minimum force necessary up to and including "Deadly force". Was the punch the minimum amount of force necessary? Probably not, but it wasn't much more than what was necessary.
I was in a similar situation when I was in the desert and that situation called for a butt stroke to the head series. He wasn't resisting over jaywalking though.
