it’s a private business that serves its clients.
it’s not a “place of public accomodation” like a park or rental space.
further the way to get around this is either to state clearly they don’t have the expertise/skilset to properly do (whatever), or state that that kind of thing falls under their advanced/special services area, which costs a minimum of at least $100,000 to start. they do have the right to specify special services and special packages and set the price however they want, nobody is forced to buy it. Unless businesses can’t determine what they consider normal or special services, and can’t set their own prices anymore.
Last I read, Both Freedom of Expression and the 13th Amendment are applicable. He has the right under the 1st to express his religion and Hobby Lobby confirms it applies to his type of business. As far as forcing him to labor for another against his will, with no contract for specific performance it would violate the 13th. It involves personal labor not just the selling of a fungible good.
“they do have the right to specify special services and special packages”
Interesting argument. Say they did charge $1000 extra for a gay cake. The gay couple would argue that is discrimination also. The bakers could then argue then that gays are the same as everyone else, they require no special cake. The bakers then claim they choose not to serve them for personal reasons, which they have a right to do as private business owners.