That suggests they can behave as they like. Good behaviour is a two way street. As a business owner I would blacklist this customer and tell him to take his business elsewhere. At that point he is no longer 'paying your wages'.Not disputing that, however at the end of the day they "pay your wages"!
Some customers are simply not worth having, the money is not worth it.
I've done this with abusive customers previously and would have no hesitation in doing it again in similar circumstances. Very rare but it does happen on occasions. Damned satisfying I can tell you and better for your mental health not to have to deal with unpleasant people.