i am late to the party but that’s the story of my life 
so, okay—NO. no there are no LOGICAL arguments against non-hetero marriages. even the religious-based arguments don’t make sense to me, because we’re not talking about two women walking into a church and wanting to wed. we’re talking about two consenting adults looking for legal protection of their partnership and commitment to each other. separation of church and state my ass.
personally, i’m not even that comfortable with civil unions. yes they’re better than nothing, but settling for better than nothing and not true equality makes me think that it’s almost admitting that non-hetero couples are NOT equal to hetero couples, and accepting this “special right” (which is really what it is if you’re not getting a true marriage out of the deal with the same terminology and everything).
i wondered if any hetero couples have gone in and requested a civil union rather than a marriage. and what would happen if they were denied the CU, and told they had to be married instead. wouldn’t that then be special treatment? or a better argument. if i were in such a state/position, i’d love to find out.
i simply do not understand where the harm is in allowing non-hetero legal unions. i mean, SO WHAT? seriously—what will happen if adam and steve are allowed to get a marriage license? how is it any different than dick and jane? they’ll still be paying their taxes, they’ll still be voting in the same elections, shopping at the same supermarkets, arguing about the same things over washing dishes, live in the same homes, drive the same cars… as if they weren’t “married.” i just DONT GET IT.
man this frustrates me to no end. that must have been while i felt compelled to respond