Benjamin Shapiro, a Shillman Journalism Fellow at the Freedom Center argues against David Frum's abdication of defending marriage:

What was Frum’s justification for his shift from traditional marriage advocate to same-sex marriage friend? “The short answer is that the case against same-sex marriage has been tested against reality. The case has not passed its test.”

... This, of course, is supremely idiotic. Same-sex marriage has not been tested nationwide. It is sanctioned by the government in precisely six states now: New York, Massachusetts, Connecticut, Iowa, Vermont, and New Hampshire. California is on the fence. Not much of a sample size.

...nobody is accusing same-sex marriage of being the sole determinant of marital decline. But it is a symptom of a broader devaluation of marriage. The same people who push for same-sex marriage push for registered partnerships, for civil unions – for governmental benefits for non-traditional marriage. As those legal situations become more available, more people will take advantage of them, and less people will buy into traditional marriage. We’ve already seen it in the Netherlands, where the number of marriages has declined consistently since the legalization of gay marriage; it’s down 10 percent since 1999. Meanwhile, registered partnerships have exploded 500 percent over the last ten years. According to William C. Duncan of the Institute for Marriage and Public Policy, “Nine in ten couples plan to live together before marrying and two-thirds of cohabiting couples plan to marry ‘but keep postponing marriage.’”