Does a bartender have the legal right to turn a customer away if there is no birth date on their ID?

This is something of a specious question, since most bartenders, restaurants, and clubs, are under legal obligation to check for a valid ID with a birthdate on it in order for any individual to be served alcohol. Regardless, nearly every businesses - - at least in the USA - - has the right to turn away anyone for any reason; this is not a "legal" issue, as much as it is a civil right, though, of course, there might be local and Federal laws which specifically prevent businesses from turning away people based on their sex, ethnicity, handicap, etc (obviously, every business is different). In this case, it is incumbent on the customer to have proper ID in order to be on the premises and/or consume alcohol there, and it is the legal requirement (in most States) for the bartender/host(ess)/owner to check for such ID, so, the law would be on the side of the bartender, et al., if he/she refused to serve a customer who didn't have a valid ID.