Lawyers decline clients all the time. Then again, lawyers right and decide the laws.
Funny how lawyers are the only ones with that freedom.
But they don't do it because the client is black, gay, Muslim, disabled, or any of the other protected classes. This photographer can refuse to take child porn pictures, or Halloween party pictures, or pictures of an auto show or things like that because it isn't illegal. Refusing to serve a customer because they're black or gay is. The courts need to finally determine where someone's rights to practice their religion ends and the rights of the protected class client begins.