Now that homosexuals walk away with two victories from the Supreme Court, Kent Greenfield, writing at the American Prospect, acknowledges that once you accept the arguments in favor of gay marriage, you cannot honestly argue against allowing polygamy or, even, incestual marriages.
The left is in this bind in part because our arguments for expanding the marriage right to same-sex couples have been so compelling. Marriage, we’ve said, is about defining one’s own family and consecrating a union based on love. We’ve voiced these arguments in constitutional terms, using claims arising from the doctrines of “fundamental rights” and equal protection. Fundamental-rights analysis says that marriage is for many a crucial element of human flourishing, or as the Court said almost fifty years ago “essential to the orderly pursuit of happiness.” Because it’s so important, government can restrict marriage only by showing a truly compelling justification. The equal protection argument is simply that the marriage right should not be taken away from groups unless the government has good reasons to exclude those groups.
When it comes to marriage, the fundamental rights claims and the equal protection arguments often intertwine. For example, Justice Kennedy’s opinion last month striking down a portion of the Defense of Marriage Act said that DOMA’s injection of “inequality into the United States Code” violated the “liberty” protected by the Constitution. The “inequality” part is equal protection language; the “liberty” wording is fundamental rights stuff. The analytical box is not all that important. What it boils down to is that when the government wants to exclude groups from something important like marriage, it has to show good reasons for the exclusion. And prejudice—simply thinking something is “icky”—doesn’t count as a reason.
The arguments supporters of same-sex marriage have made in court do not sufficiently distinguish marriage for lesbians and gay men from other possible claimants to the marriage right. If marriage is about the ability to define one’s own family, what’s the argument against allowing brothers and sisters (or first cousins) to wed? If liberty protects, as Kennedy wrote ten years ago in Lawrence v. Texas, the case striking down Texas’s anti-sodomy law, the “right to define one’s own concept of existence, of meaning, of the universe, and of the mystery of human life,” why can’t people in polyamorous relationships claim that right as well? If it’s wrong to exclude groups because of prejudice, are we sure the uneasiness most of us feel about those who love more than one, or love one of their own, shouldn't count as prejudice?
In private conversations with leaders in the marriage movement, I often hear two responses. The first is that there is no political energy behind a fight for incestuous or polygamous marriages. The second is that they would be fine if those restrictions fell as well but, in effect, “don’t quote me on that.” The first of these responses, of course, is a political response but not a legal one. The second is to concede the point, with hopes that they won't have to come out of the closet on the concession until more same-sex victories are won in political and legal arenas.The article goes on to shoot down some of the common arguments against polygamy and incestual marriage between adults, and suggests that liberals need to either come up with some valid Constitutional arguments or admit that there is a slippery slope.