YOu want to watch a Gay person go into spasms, ask them why a father can't marry his daughter if he gets a vasectomy. The "union" meets all the gay criteria:
It can't produce children
It is all about Love
It is 2 people.
They sputter but can't answer.
Oh yeah, forgot about incest. That comes after child marriage.
Gay marriage -> polygamy -> child marriage -> incest -> bestiality