Andrew Sullivan explains like almost no one else can:
It has always seemed chilling to me that gay leftists – when pushed to say what they really believe – want to keep gays in some sort of glorious, oppressed, marginalized position, until the majority agrees with the gay left’s view of human nature, and revolutionizes straight society as well. This will never happen (and in my view, shouldn’t).
Until then, the gay left focuses on demonizing those gays who argue for those who want to belong to their own families as equals, serve their country or commit to one another for life. In this, in my view, the gay left mirrors the Christianist right: they insist that otherness define the minority, even though most members of that minority are born and grow up in the heart of the American family, in all its variations, and of American culture, in all its permutations. No one should be marginalized for seeking otherness. But we are fighting for it to be a choice, not a fate.
He was responding to this piece:
Nobody is saying gay people have to get married—only that it should be a legal option if they want it. If you disagree with marriage, don’t get married.
This is good for the U.S. to think about because just as there are many nuances and shades in different religious groups (literal factual readers of The Bible vs. metaphorical historical readers of The Bible), there are some in the GLBT fold as well.