I think if the cake maker's argument to deny making the cake is on the basis of artistic reasons, then they should be willing to make "a" cake for the customer, just not a cake that goes against their aesthetic sensibilities.


However, if they are claiming artistic reasons to not make "any" cake at all for the couple, then that strikes me as incoherent.
Well, I agree here and I think banana does to, though obviously I can't speak for him.