Will marriage that encompasses gays and lesbians undermine this?
The first thing to say is that lesbians seem to be far more eager to marry than gay men. Duh. It's not because they're lesbians, it's because they're women. It follows, however, that lesbian couples are likely to be more monogamous than most straight couples as well as more numerous than gay males ones. So adding lesbians to the mix actually reinforces monogamy as an ideal and feminizes marriage in ways that Ross would presumably favor.
Gay men? I think it's fair to say that the fact that they are men makes monogamy less likely than even straight marriages. If Eliot Spitzer had married another Eliot Spitzer, he may have had more sex on the downlow and spent a lot less money on hookers. Male-male marriages that survive are likelier to have some kind of informal level of permission and forgiveness and defensible hypocrisy on this score than most male-female marriages or female-female marriages, especially if the men marry young. I think the honesty within these relationships can actually be a good thing and can help sustain a life-long commitment rather than weaken it. But I can also see why it might worry Ross if this became publicly celebrated rather than privately tolerated. Given the way in which the straight family as a whole is involved in such marriages, I believe private toleration will likely prevail over public celebration. But the defensible hypocrisy of straight marriages may have an extra twist here.
But here's the thing: what, exactly, is the alternative in a world where openly gay people and couples exist?
Ross has never told us. But it seems to me from the logic of social conservatism that those most in danger of the social chaos social conservatives fear are those who would benefit most from being subjected to the cultural power of this institution. We know the consequences of marital breakdown for the black and urban poor: immiseration, poverty and dysfunction. We also know the consequences of a society that allows gay men sexual freedom, while denying them any social institutions to channel their love and desire: 300,000 young corpses. But the social conservative who insists that the family is vital for the black underclass somehow believes it is just as vital to deny it to gay men. In fact, social conservatives are intent on preventing this integrating institution from helping, guiding and ennobling a group most vulnerable to the consequences of emotional and sexual chaos. (David Brooks is a clear example of someone on the right who has actually grappled with this incoherence, which is why he supports marriage equality).
So we return to the actual world of modern reality, rather than the abstract ideology that Ross seeks vainly to re-impose on the planet from some vantage point in the 1940s. For Ross' ideology is premised, as Eve's is, on the notion that there is no need to find an answer to the questions that arise in a society where a visible, open and clear minority are proudly gay. It is premised on an era of the closet that simply no longer exists and cannot be reimposed without enormous cruelty and more state power than any real conservative would tolerate. And notice how this ideology of marriage must inevitably express itself in reality in the example of Eve Tushnet: gays have to be celibate their entire lives. We have to cease to exist, really, as sexual beings. That could never be the case in fact - hence the appalling pain and cruelty and misery homophobia inflicted on countless human beings for centuries. But now it is impossible even to pretend that this could be the case. And yet here is Ross still trumpeting it.