Suppose the custom cake bakery owner is black, and a customer asks for a cake with a confederate flag design? There's nothing illegal about the confederate flag, so the baker should be compelled to bake it, right? There isn't even a basis for refusal based on religious grounds.
I would want the black baker owner to be able to not only refuse to bake the cake, but to also tell the customer to take a hike and never return.
> so the baker should be compelled to bake it, right? There isn't even a basis for refusal based on religious grounds.
No. Because "supports the confederacy" isn't a protected class.
As far as US law goes, you can generally refuse a service to anyone for any reason, unless that reason is related to a protected class to which the person belongs, unless you have some other exception (almost always religious) for not doing the thing.
As you say protected class is a very US specific, but even there it actually depend on the state as they can and in some places has extended it. Protected class under federal law is one list and protected class under state law is an other.
Protected class does also not mean that everyone else if a free target for discrimination, and for international companies there is the European Convention on Human Rights. Refusing service based on politics require the company to do a quite complicated dance around a long list of laws and I doubt any company lawyer would be very happy to give a green light for it.
I would want the black baker owner to be able to not only refuse to bake the cake, but to also tell the customer to take a hike and never return.