If you think that marriage is the union of a man and a woman, then you are a vile, twisted, depraved bigot who simply wants to demean, humiliate and oppress Gays and Lesbians. That's pretty much accepted as axiomatic now. Fine. People are idiots. I just cannot take this equation of basing marriage on sexual complementarity with an irrational, sadistic animus towards homosexuality seriously. You know why? The two have nothing to do with one another. Even John Corvino admits that the question of same-sex "marriage" is entirely separate from whether or no homosexual relations are immoral.
Also, if basing marriage upon sexual complementarity necessarily entails homophobic bigotry, then, please, please, please, explain to me Ancient Sparta. In Ancient Sparta homosexual relations were not just tolerated, not just accepted, not just celebrated, but relied upon as a way to maintain morale in its army. Sparta was at the very top of the Riddle Scale; gay relationships were deemed literally indispensable for the existential defense of the city. And yet Sparta never ever understood marriage as anything other than the union of a man and a woman. So, the Spartans according to what passes today as Enlightened Reason must have been irrational homophobic bigots even though they did the very thing the Riddle Scale says you must do to be entirely untainted by homophobia, i.e. treat homosexuality as indispensable to the well-being of society.