Violence is never the answer BUT if a stranger comes up to you and starts grabbing you sometimes you gotta do what you gotta do.
Justin Bieber was in Barcelona yesterday and he punched a guy in the face.
Bieber was in his car going to the venue he was supposed to perform at with the windows down and a guy ran beside the car, put his hands inside and grabbed Justin. In the video from TMZ you can see the guy ended up with a bloody mouth.
Maybe Justin overreacted but if a stranger came up to me and started grabbing me I probably would have done the same thing.