I will be honest with you, in the USA “back in the day” it was a lot more than just conservatives who were opposed. And, it was an order of magnitude more people who would have been completely okay with things if it had never become legally recognized.

It was very common to hear people who were otherwise completely okay with gay people and who treated LGBT+ folks well say things like “why do they need to get married” or “I think they should be able to get civil unions but marriage is between a man and a woman” or all manners of other arguments for why. And let’s not forget that the current situation with legally recognized same-sex marriage was not due to the will of the majority of the voting public. It was via the courts.

While I appreciate the allies and all the people who aren’t / weren’t out there actively opposing gay marriage in the USA, and I completely acknowledge that lots of people have probably changed their stance on the issue in the ensuing decade+, I’m not going to fool myself into believing it was only conservatives who needed to hear the message in this meme.