I think some folks are conflating two different aspects of the whole nature vs nurture debate . . .
1) Homosexual behavior is normal, and it is natural. We have scientific evidence of this not only in the human species, but in many other species. In humans, the base of sexual attraction is genetics, it is a inherent part of who we are, hetero or homo.
2) However, gender and sexuality, like all aspects of human behavior, is a complex mix of genetics, epigenetics, cultural mores, and individual personality. How a person's base gender and sexual attractions are expressed is highly influenced by culture and upbringing. Thus, the ancient Greeks who put a premium on the male identity, but separated that from sexual attraction and behavior.
Heterosexuality truly is the "norm", most folks identify with their birth gender and are attracted to those of the opposite gender. This is a good thing, as it allows us to dominate ecosystems and overpopulate the planet, affecting global climate change . . . . . wait, sorry, I'm drifting . . . . anyway, it allows us to continue as a species.
This does not mean, however, that homosexuality or transgenderism is unnatural, aberrant, and wrong. It's just not the norm. In fact, there are theories that homosexual behavior is a natural response to overpopulation, which we are certainly experiencing as a species (not sure how widely accepted that is within the relevant scientific communities).
In the United States (and elsewhere in the world), we pride ourselves on majority rule with minority protections, that all people have certain inalienable rights to freedom and the pursuit of happiness and all of that . . . except when we don't. We too often let fear drive us to discriminate and deny rights to those who are different, whether it's because they have different skin color, different religious beliefs, or different gender orientations. Sometimes the discrimination is obvious, like when we pass laws actively discriminating against minorities (like gay people being legally barred from getting married), often times the discrimination is more subtle, like non-hetero folks not seeing themselves being represented in entertainment media (movies, books, roleplaying games).
I applaud WotC for taking the progressive stance against this subtle discrimination, and it draws me in tighter as a loyal customer. I'm also positive that the small blurb that has created this mammoth thread has also driven some folks away from D&D (at least, the official stuff) who are too uncomfortable making allowances for those who are different. But I think that WotC has come down on the right side of history on this one, and will see more gains than losses in both fan goodwill and long-term profits and sustainability of the brand.