I think it IS worth hurting someone for. I don't mean it's okay to beat the snot out of them and continue to ground and pound while they're unconscious, but a slap wouldn't be out of order. Myself, I found that just saying 'no' or 'don't touch me' or just a push brought the most extreme reactions. One dude raised his fist to me (a former friend I used to kickbox with, no less) another one grabbed a stool and threatened me with it while his friends guffawed.
You should be able to sort it without violence which does usually escalate. Can't you find nicer friends?
Lol, this is one A hole I'm talking about. I don't usually hang with people who like to sexually harass and threaten me with violence
Better to tell him really loudly, in public, not to ever touch you again. Make your feelings known without losing your temper. If you lose your temper then his friends with find it funny and he'll be able to continue. You've always got the police