While I think that anyone should be allowed to discriminate against anyone they want to in private forums (i.e. restaurants or businesses), laws prevent you from discriminating on the basis of sex although not appearance (with the exception of a few states) or if the position is covered under the Bona Fide Occupational Qualification exception. That being said, "being an asshole" isn't a covered category under anti-discrimination law, so they're perfectly allowed to discriminate all they want.