It's obvious simply by studying human behavior that gender roles are not completely artificial. And as far as homosexuality being "natural" well, that's beside the point. The point is that we need to treat all our citizens equally if they aren't comitting any crimes.
No, I'm not a Democrat. Not even close. But I believe in fairness and I believe in the Constitution. And I don't believe Democrats "have to believe" in ridiculous statements like the ones on this list.