That alone shows you that he is in the wrong job. He is not just dealing with some fan, he is dealing with one of his paying customers! He shouldn't loose sight of that so easily. It is so unprofessional to response with such sarcasm.
Plus his 'wannabee' fan celebrity status and fan interactions have actually done more harm than good when you look at it objectively. Fan interaction is fine as long as you are aware that he is also your customer!