You know, I own a music store, and there are "off" days when I would really rather not be a nice person to my customers. However, I can smile and normally after they leave, I feel better for having done it. I really don't see any reason for him to have been rude to you in the first place.
Now, having said that, I don't really expect my employees to be treated badly by customers. We have a rule here that when things get unpleasant, they are to go to some other employee and pass the customer off to them BEFORE things get rude. Sometimes, things just get started off on the wrong foot, normally because of misunderstandings.
Hopefully the guy will realize that you attract more flies with honey than with vinegar!!!