I'm getting tired of seeing this interracial marriage argument here: they are in fact completely different. The movement against opposition to interracial marriage was an acceptance that there was no substantive difference between a black man/white man or black woman/white woman. One cannot say that there is "obviously" no substantive differences between a man and a woman, even if we restrict our consideration to the context of love. You can certainly argue that there aren't, but this conclusion does not follow from the conclusion regarding interracial marriage.