No, it's that marriage is defined as hetero, which is something people care about and which they don't want to include other random groups of people into.
It's like letting furries into Star Trek conventions for the sake of "convention equality". It just doesn't work, it's an artificial equality, between things that weren't actually unequal in the first place.
sorry to burst your incompetent topaH' warp bubble, but furries are an official part of Star Trek canon. argument destroyed; theragen gas thread, exile OP to Rura Penthe