Back in 2006, in the book The Meaning of Marriage, Robert George argued that,

As a matter of subjective preference, people can commit themselves to fidelity and enter into loving, long-term, monogamous relationships that mimic what, on the traditional understanding of marriage, they have strict moral reasons to do.  But the key thing to see is that on the lifestyle liberal conception, there are no such strict moral reasons.  Even the choice of fidelity is an emotionally motivated subjective preference.  And that, I submit, explains why people who reject the traditional terms of marriage—even for putatively conservative reasons, for instance, to make the good of marriage available to people who prefer sex with partners of their own sex, find it impossible, in the end, to condemn promiscuity and the like, except, occasionally, on pragmatic grounds.

Turns out he was right.

Gay marriage is not an isolated issue.  It will eventually completely destroy the entire institution of heterosexual marriage.  An article in The New York Times explains why.

The article tells about a gay married couple from the Bay Area who intentionally did not mention fidelity and monogamy in their wedding vows.

The article goes on to explain that,

A study to be released next month is offering a rare glimpse inside gay relationships and reveals that monogamy is not a central feature for many. Some gay men and lesbians argue that, as a result, they have stronger, longer-lasting and more honest relationships. And while that may sound counterintuitive, some experts say boundary-challenging gay relationships represent an evolution in marriage — one that might point the way for the survival of the institution.

According to Denny Burk,

What is stunning here is that the report suggests that monogamy is not just a problem for gay “marriages,” but for the institution of marriage itself. In other words, they are saying that heterosexuals should also consider abandoning monogamous marriage. As one “expert” put it, “The traditional American marriage is in crisis, and we need insight. If innovation in marriage is going to occur, it will be spearheaded by homosexual marriages.”

Be sure to read Burk’s full article here.