Oedipus & Civil Unions

A few months back my Pre-K son and I were joking around, at the time he was always talking about "marrying Mommy," oh Oedipus can you hear me, I guess some of Freud's cocaine fueled stabs in the dark actually hit the mark, it's funny reading about something Freshman year in college and actually seeing it happen in the flesh, anyway he knows that he gets my goat by saying he's married to Mommy, and we get into a "No, I'm married to Mommy," "No I'm married to Mommy," fight.
So I thought I'd throw him a curve ball and say, "Well I'm married to Matteo(my toddler son)," to which he responded, "A boy can't marry another boy!"
Arghhhh, well no they can't in most places, but there are civil unions, what if he says that in pre-school in front of the teachers, or worse in front of the kids with gay parents, they'll all think we're homophobic, filling our son full of hate, we're not homophobic, we lived in San Francisco for seven years and the old "some of our best friends in college were gay," but he saved my melt down by saying, "Well I guess if they can't find a nice girl they'd like to marry it's okay for a boy to marry another boy."
YES, he shoots, he scores! We conveyed our open-minded belief system without having to beat him over the head with barely age appropriate conversations.