Your imaginary left seems to do all sorts of nutty stuff. Is it ethical to treat one's fellow man with respect and as an equal under law as well as being indicative of sound business sense? You bet.
People are going to believe what they want based on their life experiences. If they want to believe in something and live their life peacefully, go for it, why should that bother anyone. If they want to believe in something that causes them to be superior to others and violent along the way, that should bother everyone!
I want to start a Peyote Church in my basement tomorrow, you think the gov will let me... btw, I am not of Indian decent, not that race should matter .
Nevertheless, Natty, there is no justification imaginable for forcing someone to do something for anyone else that he doesn't want to do, and his right to refuse to do it must be upheld in a FREE society! Question: Should a Jewish-owned bakery be forced to bake a cake celebrating the Nazi Party, with a nasty, big swastika on it, just because somebody came in and ordered one...? Of course not!
As a theory I can accept that. As a reality, having run my own business for years and put my own personal prejudices aside. I have regularly contracted with the Heritage Society and for a few right-wing politicians with nary a qualm. I have had cordial dealings with those whose political ideology I find distasteful and have tried to provide my services with the same professional, conscientious dedication that I would extend to a paying client that I happened to find politically compatible. Does that make me a hypocrite in the minds of some? Probably, but I don't care. Treating everyone equally, and with respect has never caused me any regrets. I don't think any baker should be forced to depict racist iconography. If a Nazi were just ordering an ordinary wedding cake with no ideological message, why not?
Nothing saying that the religious person has to partake of the activities you mention, or even look at those activities. So, unless two naked gay men come into your bakery doing the baby elephant walk, you should not be able to discriminate.