Actually it kinda is what you are suggesting, Vylo.
The fact some homosexuals consider themselves to be Christian, doesn't change the fact that according to the religion they claim to be a part of, homosexual behavior is considered sinful.
If the baker refused to bake say cookiees for some generic celebration because the person making the request happened to be gay, then the baker would be practicing discrimination towards gays.
However, this is over the baking of a cake to be used for a specific event that celebrates and "legitimizes" a behavior that the baker considers to be sinful due to his religion. So by not finding fault with how the baker was treated, you are essentially saying that African American bakers should be forced to bake cakes for KKK induction ceremonies.
Okay back up a second, is Atheism a religion or isn't it, cause I've heard people try to have it both ways.
Then I guess African American bakers need to start baking cakes for KKK induction ceremonies. You can't have it both ways, Vylo.