Imagine for a moment that you are a Jewish baker who owns a small bakery. One day a couple enters your establishment and orders a wedding cake to be adorned with swastikas and the likeness of Adolf Hitler. They explain that they are neo-Nazis inspired by the marriage of the Reich Minister of Propaganda Joseph Goebbels, attended by the Führer himself. You are of course offended and decline the job. Is it your legal right to refuse service to a neo-Nazi couple? If you answer in the affirmative, would you apply the same reasoning to a gay couple who requested a wedding cake adorned with two men or two women? Are these not the same moral and legal issues?
I think not. Discrimination on the basis of what you believe versus who you are constitutes different moral categories.
http://www.skeptic.com/eskeptic/15-04-29/