Here's the lead of Andrew Sullivan's 1989 article making the case for same-sex marriage for the first time in a prominent American journal. It argued for a principle that few found compelling at the time but that most now endorse. But precisely because it was written at a time when the argument was so unfamiliar and so unpopular, it's extremely tight and persuasive — zeroing in on one key point: If not equal marriage rights, then what?
Last month in New York, a court ruled that a gay lover had the right to stay in his deceased partner’s rent-control apartment because the lover qualified as a member of the deceased’s family. The ruling deftly annoyed almost everybody. Conservatives saw judicial activism in favor of gay rent control: three reasons to be appalled. Chastened liberals (such as the New York Times editorial page), while endorsing the recognition of gay relationships, also worried about the abuse of already stretched entitlements that the ruling threatened. What neither side quite contemplated is that they both might be right, and that the way to tackle the issue of unconventional relationships in conventional society is to try something both more radical and more conservative than putting courts in the business of deciding what is and is not a family. That alternative is the legalization of civil gay marriage.
This was a great question in 1989, and it's a great question in 2015. The more you think about it, the more you are relentlessly pushed to the conviction the Supreme Court reached today. If not marriage equality, then what? An endless series of ad hoc decisions about in what respects same-sex couples should and shouldn't receive the same legal treatment as married couples? A parenthesis attached to every single law, regulation, and corporate policy saying "or gay couples in a registered civil union"? For what purpose?
If you're not going to ban same-sex relationships, then you need to offer them some form of legal accommodation. Offering the same legal accommodation that exists for heterosexual relationships is a much simpler, much fairer solution than any alternative.
In the 25 years since Sullivan wrote that article, opponents of his viewpoint have raised many objections, but they've never put forward a coherent alternative view of how things should work.