The greatest missive exported by same-sex marriage proponents is that any and all opposition to same-sex marriage is based on irrational and religiously-based prejudice. To dispel this thesis, The National Organization for Marriage has excerpted an interesting article from Melanie McDonagh from the UK Spectator:

…In other words, objection to gay marriage isn’t about religion at all and the letter that the bishops are sending to Catholic churches does, to do them credit, make that clear.

It’s all to do with the nature of marriage. And that is, a natural institution providing the optimal situation for raising children. It’s vulgarly biological, marriage — a state for bringing up children in. And that’s how it’s been for almost all of human history. Even in ancient Greece, which practically invented homosexuality — alright, it was especially about the Socratic master-pupil relationship — reserved marriage for men and women, for the conceiving and bearing of children. And it’s that fundamental character of marriage which makes it essentially heterosexual. It’s to do with the complementarity of the sexes. Men and women fulfill different roles when it comes to the rearing of their offspring, and even in an atypical family like my own, in which I’m the sole breadwinner, those complementary roles make sense. Children relate differently to mothers and fathers; they pick up cues about how the sexes work, even children who go on to become gay. And departing from that biological foundation for marriage is a radically new departure.