Another consideration to ponder, in the cases that I'm aware of, the gay couples have been turned away prior to considerations about what they actually wanted the cake to look like, on the basis of the fact that it was merely for a gay wedding. In other words, they were refused, not for the content of the requested product, but for the fact that it was going to be used in a gay wedding, which means that the owners of the bakeries wouldn't have had a chance to assert a First Amendment right to a claim of free expression. It strikes me that there is quite a difference between being forced to bake a cake to be used in a wedding ceremony and being forced to write some particular thing upon said cake.