I think you would have to have a point for me to miss.
Being a party pooper for refusing a drink because you are an employee of the establishment serving said alcoholic beverages is completely an off base statement. I have worked at said establishments as a bartender and have refused many drinks because it was not allowed to drink on the job. I have also worked at establishments where drinking on the job was overlooked and/or not frowned upon.
One thing to keep in mind is as an employee drinking on the job presents several liabilities for the employers of these establishments. I'm sure a drunk bartender slicing lemons and limes cuts themselves may present a problem if a workmen's compensation claim is filed. Also, drunk employees tend to act like drunks and make mistakes such as over pouring alcohol in drinks, making mistakes on the cash registers, possibly offending customers, etc.
Now if in fact a band is technically an employee of the establishment, members of the band should refrain from drinking as well. Is it appropriate to pay a band to perform drunk, and possibly have members of the band succumb to the behaviour some drunks display?
I honestly do not feel it is hypocritical (I think that's the word you intended not hipocrical) to refuse a drink as an employee of a business that serves alcohol and provides a place for people to party. I think your logic behind this thinking is wrong. I find your whole original post almost comical. It's a shame that we live in a world where offending people is something we have to worry about constantly. Especially when it comes to something as trivial as alcoholic beverages. Wouldn't it be nice if we could just be able to politely say "no thank you" and that ends the conversation? But no we have to worry about offending everyone these days.