I don't see how you were an ass in the way you handled this. This person was out of line by basically asking you for a favor because he's a friend of your brother. He needed to be set straight, and you were clear in doing that. The only suggestion I have is that when he texted you, you might have answered something like this: "I don't work for beer. I'm a professional and I get paid in money." That would have settled the whole issue without leaving it hanging there.