Your analogy is flawed in that you're equating biological race to religious beliefs (black dental work =/= gay marriage rights).

Look, a big reason a lot of conservative Christians oppose gay marriage is because of the consequences it'll have on the sanctity of eternal matrimony (the credibility of which is yours to debate to your heart's content, but doing so in this context will likely be seen as a strawman) and the impact it'll have on raising well-rounded children to then carry on the generic legacy of their parents, ad infinitum. If a lesbian couple raise a young boy, the notion that he'll grow up sensitive, emotional and feminine is a very real fear. If he doesn't have a strong male role model at some point in his life to teach him how to be a man, he'll take the only examples he's ever known: that of a woman.

The same holds true for a gay male couple. If they raise a little girl, the notion she'll grow up a masculine, calculating, dare I say maladjusted individual is a real fear. Sooner or later, those fathers are going to want to see their baby girl blossom into a fine young woman who is charming, attractive and modest so she can obtain a viable mate to procreate with, so on and so forth.

Nobody has a problem with gays and lesbians or which genitals they prefer to take to pound town 3 nights a week. It's granting them the same rights to raise a family and thus well-rounded individuals to carry on the future and whatever it may hold that scares some people.

Point being it's not as simple as discrimination for its own sake. It's the repercussions of granting each and every individual equal rights across the board and in all departments that has granted SJWs the kind of freedom and platform to say and act in any way they please, no matter how illogical. Some people just need to be told to shut the fuck up and get over it, plain and simple.