Favoring man-woman marriage no more "demeans" and "humiliates" other sexual relationships than favoring our Constitution demeans and humiliates the governmental systems of other countries.
Supreme Court Justice Scalia
What demeans or humiliates other sexual relationships, it seems to me (and I'm no expert), is the "business" associated with marriage. If one lets the insured choose whoever they like for their beneficiary, if one lets the dying leave their worldly goods to whoever they like, and so forth, then much of the feeling of being a second class citizen would dissipate. That would leave a clearer view of what true marriage is and might make it able to simplify any remaining debate. To put it on a very simplistic level, obviously.