I'm not speaking about Facebook at all, never mentioned Facebook anywhere in my comment or in this thread, and have not made any statements about the validity of speech restriction in any context so I'm not sure why you're mentioning that. I'm speaking to a general issue brought up by the parent.

As for your comment, the cake shop has a product they are letting people buy (in effect, serving them). They are willing to produce that product for a certain group of people for a certain activity (celebration of a state recognized marriage) based on their identity. They are not willing to produce that product for another group of people for the same activity (celebration of a state recognized marriage) based on that second group's identity. Now you can argue that the shop is within their rights to do that for religious reasons and the Supreme Court would agree with you, but it's still refusing service based on identity and you know it. If you want to split hairs and say they "refused to provide COMPARABLE service because they were gay" as the buyers may have been able to buy other products then so be it.