[U]nless Douthat is prepared to call for laws that would compel straight people to live up to the same "sexual ideal" of marriage that somehow justifies discrimination against same-sex couples—and call for laws that would punish straight people who fail to live up to that ideal (no more marriage licenses for you, Mr. Limbaugh)—then Douthat's case for discrimination is just another serving of bullshit patties (albeit a fresher one) and Douthat himself is just another conservative scaremonger scapegoating gay people for the failings of straight people.
Or as Yglesias puts it:
Instead of holding heterosexuals up to a rigorous standard of conduct—no divorce, harsh & unforgiving attitude toward infidelity—we’re going to discriminate against the gay and lesbian minority and then congratulate ourselves on what a good job we’re doing of upholding our ideals.
Yeah, that just about sums it up. Greenwald steps in:
[I]f the arguments for the objective superiority of heterosexual monogamy are as apparent and compelling as Douthat seems to think, they ought not need the secular thumb pressing on the scale in favor of their view. Individuals on their own will come to see the rightness of Douthat's views on such matters — or will be persuaded by the religious institutions and societal mores which teach the same thing — and, attracted by its "distinctive and remarkable" virtues, will opt for a life of heterosexual monogamy. Why does Douthat need the State — secular law — to help him in this cause?