Damon Linker has an interesting analysis of a brief (PDF) filed by Robert George, a Catholic law professor at Princeton, in the Prop 8 case. He notes that all this focus on having children makes contraception the real target of the arguments being used by the anti-gay side.
George and his co-authors Sherif Girgis and Ryan T. Anderson make the following argument: “Our civilization” has univocally defined marriage as a “conjugal union” between one man and one woman — that is, a union between two people that is oriented to the goal of producing children. Whether or not a particular male-female couple can produce a child is irrelevant. In cases of infertility due to medical defect or advanced age on the part of one or both members of the marriage, the union falls short of reaching its goal but remains oriented to that goal nonetheless. (The union would produce a child if the bodies of both members were functioning as they should.)
Unless, of course, contraception is used to prevent that from happening, as most couples do at least some of the time.
Any number of objections could be raised against this line of argument. (Is it really true, for example, that “our civilization” has affirmed a single definition of marriage?) But I’m primarily interested in focusing on its most decisive weakness — which is that it gets a crucial chain of causality exactly backwards. Permitting gay marriage will not lead Americans to stop thinking of marriage as a conjugal union. Quite the reverse: Gay marriage has come to be widely accepted because our society stopped thinking of marriage as a conjugal union decades ago.Between five and six decades ago, to be precise. That’s when the birth control pill — first made available to consumers for the treatment of menstrual disorders in 1957 and approved by the FDA for contraceptive use three years later — began to transform sexual relationships, and hence marriage, in the United States. Once pregnancy was decoupled from intercourse, pre-marital sex became far more common, which removed one powerful incentive to marry young (or marry at all). It likewise became far more common for newlyweds to give themselves an extended childless honeymoon (with some couples choosing never to have kids).
In all of these ways, and many more, the widespread availability of contraception transformed marriage from a conjugal union into a relationship based to a considerable degree on the emotional and sexual fulfillment of its members — with childrearing often, though not always, a part of the equation. And it is because same-sex couples are obviously just as capable as heterosexual couples of forming relationships based on emotional and sexual fulfillment that gay marriage has come to be accepted so widely and so quickly in our culture.
Which is why so many of the people who oppose same-sex marriage also oppose contraception, which is the real target of the anti-choice movement — if they cared primarily about preventing abortions, they would be advocating for the widest possible distribution and availability of birth control. Because they think God is in control of everything, especially when you have children, so any steps taken to prevent that are by definition immoral (never mind that if God were actually in control and deciding who gets pregnant, our puny human condoms and pills would be of no use).