Not very long ago all cars had internal combustion engines. If you asked someone to define a car, they might well have said something like, “a passenger vehicle using an internal combustion engine”. The engine was part of the concept of a car.
Then someone was inconsiderate enough to design a car-like vehicle that didn’t have an internal combustion engine; it had an electric motor instead. Clearly not a car by the traditional definition, so we would expect that it would be given a new name: we might call it a “civil vehicle”, perhaps, if you’ll forgive the snarkiness. (“Wireless tram” would be a more neutral option, if you would prefer it.)
But we didn’t. We recognized pretty much immediately that, while this vehicle was different from the cars we were used to, the differences weren’t really relevant: the new vehicle was, to all intents and purposes, just a different *kind* of car. It wasn’t necessary to give it a new name, or to make new road rules for it. Our conception, our *definition* of what it meant for something to be a car changed seamlessly.
In 1950, the idea of an electric car would sound outlandish; I would anticipate amusing comments about the length of power cords. Now it seems normal, and it would be surprising to find someone who refused to accept that an electric car was, in fact, a car.
That’s pretty much how SSM feels, I think, to most people that have no objections to homosexuality per se. I’m 46 years old; when I was growing up, it was widely accepted that marriage was between a man and a woman, and I accepted that without ever thinking about it. Then, around 2004, SSM became a political issue. I *still* didn’t need to think about it, or not much: once the idea was presented to me, I recognized instantly that it was just another kind of marriage, just as I recognized instantly that an electric car was just another kind of car.
(We didn’t get SSM right away, of course; the religious community was too strong at the time, and we would up with civil unions as a sort of compromise. SSM was legalized in New Zealand 19 August, 2013.)
At any rate, including SSM under my definition of marriage wasn’t and isn’t a “strategy”. It has quite simply always seemed obviously correct, and I struggle to understand why anyone would disagree. This sometimes leads me to assume that opponents have hidden motives, presumably either religious or prejudiced (or perhaps just a general opposition to any sort of social change) though I should probably avoid jumping to that conclusion. There may well be some atheist, unprejudiced opposition to SSM, and the fact that I can’t recall seeing any off the top of my head isn’t particularly significant; it probably wouldn’t be particularly visible above the general noise level. 🙂