This is getting off topic, but: I read
Masterpiece as saying that, if you're going to apply the rules against a Christian baker, you have to apply the
same rules against a gay baker (CO Civil Rights ignored complaints from Christians against gay bakers who wouldn't put some Christian message on their cake).
I think this is the right approach. A Christian could go to a gay baker, asking for a cake that quoted a Bible verse that said that homosexuality is a sin. A gay rights convention could ask a Christian baker for a cake that said "Christianity is bigotry". The rules for one have to be the rules for the other.
My preferred answer: Put a gay baker and a Christian baker in a room. Tell them to come up with the rules. The rules will apply to both of them. Give them two hours. You'll get a reasonable proposal. Make that the rules.