Haven’t heard enough reasons why legalizing same-sex marriage will ruin society? Well, here’s a new argument against repealing it: It would hurt the black family unit!

“One overpowering cause of black social failure is the breakdown of marriage in the black community. Nationally, the black illegitimacy rate is 71%; in some inner city areas, it is closer to 90%,” writes Heather Mac Donald, a former lawyer and Manhattan Institute fellow who says she believes gay marriage is inevitable. “When boys grow up without any expectation that they will have to marry the mother of their children, they fail to learn the most basic lesson of personal responsibility. A community without the marriage norm is teetering on the edge of civilizational collapse, if it has not already fallen into the abyss. Fatherless black boys, who themselves experience no pressure to become marriageable mates as they grow up, end up joining gangs, dropping out of school, and embracing a “street” lifestyle in the absence of any male authority in the home.”

Right, okay, but what does that have to do with gays getting married? (Emphasis ours):

If the black illegitimacy rate were not nearly three times the rate of whites’, I would have few qualms about gay marriage. Or if someone can guarantee that widespread gay marriage would not further erode the expectation among blacks that marriage is the proper context for raising children, I would also not worry. But no one can make that guarantee. Why might it further depress the black marriage rate? There is a logical reason and a visceral reason. First, it sends the signal that marriage is simply about numbers: it is an institution that binds two (for the moment) people who are in love. It erases completely the significance that marriage is THE context in which the children of biological parents should be raised. And there are undoubtedly many other subtle meanings and effects of gay marriage that we cannot even imagine at the moment—which institutional shift is something that conservatives should be most attuned to. As for the visceral reason: It is no secret that resistance to homosexuality is highest among the black population (though probably other ethnic minorities are close contenders). I fear that it will be harder than usual to persuade black men of the obligation to marry the mother of their children if the inevitable media saturation coverage associates marriage with homosexuals. Is the availability of homosexual marriage a valid reason to shun the institution? No, but that doesn’t make the reaction any less likely. What are the chances that gay marriage would further doom marriage among blacks? I don’t know. Again, if someone can persuade me that the chances are zero, then I would be much more sanguine. But anything more than zero, I am reluctant to risk. Is it fair to those gays who want to marry that their desires should be thwarted for the sake of black boys? Maybe not. And as has been pointed out many times before, it is exclusively heterosexuals who have eroded the institution of marriage through easy divorce, increasing rates of single-parenting, “blended” families, and co-habitation. But just because marriage is already in bad shape, for reasons wholly unrelated to gay marriage, doesn’t mean that gay marriage won’t weaken it further.

If only Ms. Mac Donald could remember a time when whites thought allowing interracial marriage would somehow destroy their unions — and not only how the moral logic didn’t hold up, but neither did the theory.