James Gardner at the Slice at TPM has a really interesting piece up about this small group of Mormon men who identify as "same-sex oriented" but are married to women. Some of them---though interestingly, not all---oppose gay marriage and have signed an amicus brief to the Supreme Court claiming that, if gay marriage is legalized, it would somehow hurt and delegitimize their marriages. The argument, like all variations of the "gay marriage is a threat to traditional marriage" arguments, is illogical and muddled, probably because they can't come right out and say what they really mean. It's clear that the real reason same-sex marriage is threatening is because these men, despite swearing up and down that they love being married to women, really would prefer it if they could marry and have sex with someone of their gender. And if the court allows other men to have what they want but deny themselves, it will cause jealousy and strain marriages that are already fragile, as you might imagine.
The whole movement, small as it is, is clearly steeped in homophobia, but reading about these couples, you also begin to see how it's also just really sexist. It's not a coincidence that the gay person in all these couples is the man. I have a feeling that even the marriage-fanatical Mormons would draw the line at pressuring straight men to marry lesbians. It's only women that are expected to be self-sacrificing enough to marry someone who openly doesn't find you attractive and to be so disinterested in sex that they'll put up with a spouse who can only be moved to fuck you once in a blue moon, mainly for dutiful reasons.
Either way, the idea that gay people have to sacrifice their rights so that a bunch of people making poor personal choices can feel slightly better about themselves is a crap argument, and I hope the court disregards it.