Ok, but that does not change the fact that the bakery in this situation was in fact discriminating. You don't have to refuse all service to be discriminating illegally.

A more sinister version of the same logic is the argument that states weren't discriminating against gay people by not letting them marry someone of the same sex because technically they could go find someone of the opposite sex and be granted a wedding license for a life of misery married to someone who they could literally never be attracted to instead of the person they were attracted to and loved. It's discrimination in either case.