They did this by talking about gay marriage in terms of fundamentally conservative values: fidelity, family planning, and all that sort of stuff. This reframed the whole gay crusade. It ended up being a powerful engine for gay rights because for a long time when you said to Americans “gay rights,” they flashed on the gay pride parade, on men in leather and on “dykes on bikes.” They flashed on people who wanted validation for what those other Americans saw as a transgressive lifestyle.

The great thing about marriage equality and same-sex marriage is it was saying, “let us enter into this very conservative arrangement, please let us emulate you. More of our values are in common with yours than in conflict.”

It took a while for L.G.B.T. people to realize what a winning argument gay marriage was.

What does that tipping point reveal about America? And how can we learn something about Australia from this?

It reveals two things about America. And I think these things were boldly underscored by the last election.

First, too much change, too quickly, frightens people — and I don’t think this is true just of Americans. It certainly frightens Americans — the sense that the fundamental paradigm of the country as they know it is being challenged or changed scares them. And so for gay and lesbian people to reframe themselves from the other to the familiar was a huge thing.

Second, and this is true in the United States and in Australia, it used to be the case that the vast majority of gay and lesbian people were in the closet, so people were thinking about gay rights as an abstraction. Gay rights were not about how much you loved and respected your sister, your son, your uncle, your cousin, your best friend from college.

Now, pretty much everywhere — I know this to be true in Australia without knowing much about the country — it’s a generational matter. If you are under the age of 50 or 60, or even if you’re older, you don’t live in a world in which gay or lesbian people are an abstraction. So when you vote in a way that seems dismissive or censorious of them, or when you vote in a way that seems to deny them a right, you process that vote now as something you are doing to your beloved friend, to your beloved son. That’s changed everything and that’s why I think 50 years from now this will all seem quaint.