You're misrepresenting me. We know that marriage between two unrelated individuals does not appear to cause significant social difficulty. There's no evidence that those two unrelated individuals being the same sex changes that, and therefore permitting a man and a woman to be married but not two women or two men is discriminatory.

Beyond that? Like I said, I don't know. I haven't considered the issue. I haven't looked for evidence regarding changes in social dynamics caused by group marriage. That's an entirely consistent position to hold.