There’s a very big story unfolding in California right now whose ultimate outcome could determine whether or not gays and lesbians will have the right to get married in the United States.

The story concerns Proposition 8, the statewide referendum banning same-sex marriage. Having failed to prove their case in court, Prop 8 supporters are now attacking the sexual orientation of the judge who overturned the referendum.

Supporters of Prop 8 were dealt a blow last year when Judge Vaughn Walker ruled that there is no empirical basis for the notion that same-sex marriages harm heterosexual marriages and therefore no compelling interest in preventing gays and lesbians from getting married.

Yesterday, same-sex marriage opponents filed a motion to have Walker’s ruling vacated, on the grounds that his being gay and in a long-term relationship amounts to a conflict of interest that should have forced him to recuse himself:

Given that Chief Judge Walker was in a committed, long-term, same-sex relationship throughout this case (and for many years before the case commenced), it is clear that his “impartiality might reasonably [have been] questioned” from the outset. He therefore had, at a minimum, a waivable conflict and was obligated either to recuse himself or to provide “full disclosure on the record of the basis for disqualification,” so that the parties could consider and decide, before the case proceeded further, whether to request his recusal. His failure to do either was a clear violation of Section 455(a), whose “goal ... is to avoid even the appearance of partiality.”

This argument is too clever by half, and relies on the same faulty argument put forth originally in defense of Prop 8: The qualitative judgment that same-sex relationships are inferior. Opponents of same-sex marriage are arguing, in effect, that because Walker was in a long term same-sex relationship, he stood to benefit personally from Prop 8 being overturned. They argue, naturally, that the issue is not Walker’s sexuality per se, but his relationship status. But by that logic the only way a gay or lesbian judge could rule impartially on matters involving gay rights is if they’re celibate.

The problem is that this same logic could be applied to a straight, married judge hearing the case. After all, supporters of the same-sex marriage ban are arguing that marriage equality is so damaging to the institution of marriage that the government has a vital interest in making sure gays and lesbians can’t get married. That means that a straight, married judge couldn’t be expected to be impartial, either — after all, according to supporters of Prop 8, “the further deinstitutionalization of marriage caused by the legalization of same-sex marriage,” would directly impact married heterosexuals. Therefore, a heterosexual, married judge could be seen as having just as much “skin in the game” as Judge Walker.

Proposition 8 supporters would never make that argument, of course, because the implication of their argument is that gays and lesbians are incapable of the impartiality expected of judges by their very nature. The notion that Walker’s ruling should be vacated is build on the flimsy assumption that gays and lesbians are different from heterosexuals in a manner that justifies denying them their fundamental rights. It’s also built on an unstated but core conservative view of the courts — that judicial “impartiality” is best defined as viewing the law through the cultural prism of a heterosexual, conservative white Christian judge. That’s partly why the impartiality Justice Sonya Sotomayor was viewed as suspect from the outset.

The real problem faced by Prop 8 supporters real problem is that their case is profoundly weak, and relies almost entirely on archaic and rapidly eroding social prejudices against homosexuality. During the trial, they only called one witness, and that witness was unable to provide a factual basis for the assertions being made by Prop 8 supporters — that extending marriage rights to gays and lesbians would harm anyone. Conversely, Prop 8 opponents were able to demonstrate, in vivid detail, precisely how they were personally hurt by California’s decision to deny gays and lesbians their fundamental rights.

Now Prop 8 supporters are reduced to arguing, essentially, that Walker’s ruling should be vacated because he is gay. Aside from the faulty legal reasoning, supporters of the law aren’t doing themselves any favors when it comes to convincing anyone that their position on marriage amounts to anything other than prejudice.

UPDATE: My mistake — Prop 8 supporters called two witnesses during the trial, not one. But neither was able to offer empirical evidence for the assertions made about the negative impact of legalizing same-sex marriage.