I think the bit most people miss here is that most of these weirdly obsessed homophobic types dont think its "just a matter between two concenting adults". Most of them, either on a consious or subconsious level believe gay marriage etc is somehow causing harm to society as a whole. It doesnt just disgust them, it quite literally terrifies them.

In the case of religeous folks, that terror can extend as far as divine retribution (i.e. floods, hurricanes, natural disasters). In non-religious folks, the terror is probably more akin to stuff like "the breakdown of law and order" or some nebulous threat of societal upheival creating chaos. But in a sense, both are effectively the same because it wont ever work to tell them to "just ignore it".

When was the last time that calmly explaining to a religious zealot that their god doesnt exist actually succeeded in convincing them?

I dont know the actual solution to this problem. At least for the religeous folks, it will have to involve religeous figures demonstrating acceptance and disavowing sects that refuse along with a lot of actual progress and exposure to get people to empathise and humanise lgbtq+ people and realise that theyre not a threat. Its possible, its actually quite easy once the balls rolling, but its a difficult thing to do to start i think.

And this is obviously not to excuse or diminish the actions of homophobes and anti-progressives. But its important to actually understand the root of the problem if its going to be possible to change them for the better in the future.