Before i make my decision on how this shop owner ‘scum’ should be punished, i need a few more details.
Were you using this cafe for food/drink or was it just somewhere to lock your bike while you went elsewhere?
What exactly is ‘mild violence’ in this scenario? Soft punches/gentle kicks or firm punches/kicks but wearing padded shoes and gloves? Tickling but using firm fingers (AKA the Tiny Punch technique). Sticky tape to the hairy part of the forearm ripped off quickly? Flicking of the earlobe?
Depending on the answers to the above the punishment could range from ‘wind yer neck in and stop obstructing the entrance to his business’ to ‘kill him and all his bloodline’. Obviously, you’d not be letting the police know either way.