On a personal level, no the baker should not discriminate. Discrimination is wrong and I don't care what your religion says.

On that same token, there is no victim here. The couple was not beaten, robbed, or killed. If they were not adequately served at this establishment, they should have found another that would place money over personal opinion.

From a political level, this should not even be an issue. The governments place, is not to tell the population how to run their day to day lives. Freedom does not mean that everyone will agree. Nor does it mean that everyone MUST agree. Freedom means that people get to live their lives howsoever they choose, as long as that choice does not impinge on the life, liberty, or the pursuit of happiness/property of other individuals.

No one told them they could NEVER get a cake from ANY baker; Merely that this particular baker, would not make one for them. To me, this is a case of hurt feelings and revenge. Nothing more.