Where does it say that you can not bake a cake for gays in the bible?
The baker thinks he is actively participating in a gay wedding by making a cake. That is ridiculous.
The baker of my wedding cake had nothing to do with my wedding and was not invited. 

“Now please observe a moment of silence so we can thank the man who made the cake for this wedding. He sanctified the wedding and made it real. With out the baker, the wedding could not take place.” Said no one ever.

The first amendment does not give you the right to break the law and discriminate.