What? States that do not recognize ss'm' forbid people of the same sex from sharing apartments? They have outlawed men's and women's restrooms and locker rooms? These states do not allow all boys' or all girls' schools? The anti-miscegenation parallel has utterly no basis in history or, more importantly, logic. Those who appeal to it simply want to mention White Supremacists and those who oppose the legal recognition of ss'm' in the same sentence so as to make people think that the latter are in the same category as evil racists. But this is not the case for the anti-miscegenation parallel is nothing more than an obvious category mistake.
Nevertheless, this analogy has come to be widely accepted as common sense simply through force of repetition. The anti-miscegenation parallel, in other words, is a textbook example of Hitler's Große Lüge, The Big Lie.