This morning, Rep. Trent Franks, chairman of the House Judiciary Subcommittee on the Constitution, called a hearing on “Defending Marriage” to examine the Obama Administration’s decision to stop defending the so-called “Defense of Marriage Act” in courts.

Franks is pretty, um, far to the right, so it’s no surprise that one of the three witnesses he called to the hearing was Maggie Gallagher, chair of the National Organization for Marriage.

As Justin wrote earlier, Gallagher hit a bunch of the big themes of the Religious Right’s anti-gay activism, but she also dwelled on one argument peculiar to the anti-marriage equality crowd: that marriage exists solely as a structure for procreation:

If we accept, as DOMA explicitly does, that this is a core purpose of marriage, then treating same-sex unions as marriages makes little sense. If marriage as a public and legal institution is oriented towards protecting children by increasing the likelihood they are born to and raised by the man and the woman whose union made them, then same-sex couples do not fit. If same-sex couples “fit” the public definition of marriage, then marriage is no longer about responsible procreation. Same-sex marriage cuts marriage as a public idea off from these deep roots in the natural family. Over time the law will re-educate the next generation that these ancient and honorable ideals underlying marriage no longer apply. Gay marriage, as Judge Walker ruled in wrongly striking down Prop 8, is based on the idea that neither biology nor gender matters to children. Same-sex marriage repudiates the public’s interest in trying to see that children are, to the extent possible, raised by the man and woman whose bodies made them in a loving single family.

The argument that marriage exists solely for having children is, needless to say, flimsy – and has been pretty well demolished in a few marriage equality trials. I’m just going to share this extended exchange from last year’s Proposition 8 trial, in which Judge Vaughn Walker reduces the lawyer defending Prop 8 into babbling incoherence as he tries to defend the marriage-is-only-for-procreation argument:

THE COURT: And my point was that there are a number of heterosexual couples who do not naturally procreate, who require the intervention of some third party or some medical assistance of some kind.

MR. COOPER: Yes, your Honor. And it is not those opposite-sex couples either that the state is concerned about in terms of — in terms of the threats to society and the natural concerns that society has from irresponsible procreation.

THE COURT: What’s the threat to society of people choosing to have medical assistance in order to conceive children?

MR. COOPER: There isn’t one there, your Honor. I mean, it’s — it is the — again, it’s irresponsible procreation. The procreation that comes about casually. And often again, as the Eighth Circuit put it, often by accident, unintentionally, unintentionally. The opposite-sex couple where one of the partners is infertile, for example, or the same-sex couple can’t unintentionally procreate, but for reasons that we discussed earlier with respect to the opposite sex but infertile couple, allowing them to marry isn’t something that is inconsistent with the purposes of — the core procreative purposes of marriage and, in fact, in certain respects it advances those purposes and it would just not be possible or realistic, as case after case has said, for the state to try to implement its policy on a more narrow or fitted basis.

And, your Honor, with respect to — and you asked a question about this in your written questions. Even with respect to the opposite-sex couple where one of the partners is infertile, encouraging that couple to get married, trying to channel that couple into marriage furthers the procreative purposes and policies underlying the traditional definition of marriage in the sense that if that couple gets married, then it — then all of the social norms that come with marriage to encourage that couple to stay together and to be faithful to one another operate to society’s benefit in the sense that the fertile member of that couple will be less likely to engage in sexual relationships with third parties and raise anew a threat of some type of unintentional or what I have been referring to previously as irresponsible procreation.

THE COURT: Why don’t those same values, which are values to society that you have described, apply to lesbian couples and gay couples? Coming together, supporting one another, taking care of one another, looking out for one another, being an economic unit, being a social unit, providing love, comfort and support for one another, why don’t all of those considerations apply just as much to the plaintiffs here as they apply to John and Jane Doe, to use the names that Reverend Tam used.

MR. COOPER: Those purposes, your Honor, are – we haven’t suggested there is a distinction among gay and opposite-sex couples with respect to those considerations. There is a distinction, however, with respect to the fundamental procreative purpose, responsible procreative purpose of marriage; and that is that the gay couple, unlike the opposite-sex couple where one of the partners may be infertile, doesn’t represent — neither partner in the – with respect to the same-sex couple is — again, assuming homosexual sexual orientation — represents a concern about irresponsible procreation with a third party.

To summarize, Cooper, when pressed on the issue, ended up arguing that opposite-sex couples should get married so they don’t go around “irresponsibly procreating” with people they aren’t married to…but same-sex couples aren’t in danger of irresponsibly procreating, so they don’t need to get married….and that somehow, if gay couples were to get married, they would drive heterosexuals away from marriage, resulting in them having babies out of wedlock.

To be clear, this is the primary argument that opponents of marriage equality have in their toolkit.