The Right and Sex
One of the things that strike me about conservative arguments on homosexuality, is that they tend to focus almost exclusively on the biological aspects of sex.
Here's another piece bashing the idea of gays having children. It all revolves around biology: sex is about producing babies, gays can't do that through "natural" means, so this must be immoral. The idea of basing the morality of an act on this premise is odd.
Because there's nothing moral involved with biology. If there were, animals that produce an infinite number of offspring would be the most moral of creatures. The whole point of the Christian tradition is that there is something in us which is not simply animal, biological.
Rather we're created in the image of God, blessed (and sometimes cursed) with the possibilities of self transcendence, such that sexuality if it takes on any moral character will be more than simple biology. It ought to be a reflection of certain ideals and values that are choice worthy.
One hopes that the gay marriage debate actually does change our views on sexuality, not from norms to no norms as the right alleges, but from accident and biology to love and mutuality. Several feminist sites are working out what this means in helpful ways.
"And since homosexuals insist upon desiring limitless sexual activity, not governed by provincial rules and traditions, why would they want children?" This is the picture that the right lives by. Gay marriage is so scary for them because it ends up undermining this picture.
In many ways gay and lesbian parents are probably more mindful than the right because there's a valuing of marriage and children beyond biology. This may be a rejection of provincialism, but not of norms. It's from that context that more appropriate norms will develop.