Portland area during a rainstorm. He received no tip, so he yelled something at the customer as he was driving away. The customer then called the restaurant to complain. When my acquaintance got back to the restaurant, the owner chastised him for calling out the customer.

This just incensed him even more, so HE WENT BACK to the customer's house, knocked on the door, and when it was opened, chewed out the man, and said his wife was a fat pig. The customer proceeded to beat the snot out of him.

My acquaintance didn't fight back at all, because he already had an assault arrest under his belt. He didn't even seek to press charges, not that the police would have pursued it if he had.