I believe that any business should be allowed to deny service IF AND ONLY IF there is a LARGE sign in BOTH the front window or on the entry door of the company (as well as at the register) that lists those groups which will be denied such service. I'm betting that none of them (including the baker in question) would be willing to make that announcement, considering the percent of folks in the US who now believe that it is no longer anyone's business as to the sexual orientation of a person/couple (not to mention any other reason for discriminating against folks).