You shouldn't beat someone up.
Bob is at a bar when a drunk customer begins making trouble in the bar, threatening people with a bottle.
Bob wants to protect the customers.
Bob lunges at the customer, takes away the bottle, and pins the customer to the ground.
Bob charges the drunk customer, disarms him, and punches him repeatedly.
The customer is very angry but unharmed and is escorted out of the bar.
The customer is badly wounded and reports Bob to the police, who then arrest Bob.