So if you can't fight genetics...explain vegans. Humans are genetically designed to eat more than just plants and vegetables, and yet there are many, many humans that defy genetics and do just that.
So if homosexuality is unalterable...explain Anne Heche. She was heterosexual, then lesbian, and now once again heterosexual.
To borrow a line from "The Princess Bride", I don't think those words (genetic/unalterable) mean what you think they mean.
Which explains why Bill Walton's career was shorter and less productive than his coaches and contemporaries expected. He needed protein, but he denied himself his needed nutrition.
Therefore I explain vegans as the latest iteration of millenialists, religious enthusiasts, Hesychasmists, Lollards, Gnostics, Sufi dervishes, and Solar Temple acolytes, all of whom firmly believe things contrary to fact or contrary to nature. Moonbats, we sometimes call them.