“Is not having sex before marriage a grave sin against the Lord? Do these same bakeries make cakes for a couple who are living together in sin before marriage?”
Not really a good argument. The baker never said he wouldn’t bake a cake for gays, only that he would not bake a cake in celebration of their “wedding”. The argument would be that he might bake a cake for fornicators, but not one to celebrate their living in sin.
So if a gay couple go into Christian bakery and just ask for two men on the cake vs. the traditional man and woman, would the baker still refuse to bake the cake? In that example, the baker is not being asked to “celebrate” the marriage but would be decorating the cake as part of being a cake decorator. Right?