"They wanted him to participate in and condone a marriage his religious beliefs don't allow, that's the difference."

What are you even talking about?  How is having him make simply make a cake equate to "participating" and "condoning" a marriage?  

Does this same baker ask his straight clients if they have ever been Divorced before, or if this is their first marriage?  Does he give every single one of his potential customers a checklist that they must go through to make sure he only sells his goods to people that conform to his specific religious beliefs?  No - he just wants to discriminate against gays.