Not just gay marriage. Dude is flat out anti any premarital "sexual conduct".
I don't mean to diminish the very real threat the GQP poses to our LGBTQ+ posters, but I want to focus on the implications of that broader statement. Saying pre-marital sexual conduct is evil and that states can discourage it is extreme Christofascist bullshit.
Also he's a lawyer who is watching his language. He's usually very precise in how he says things. Note he didn't just call out premarital sex, he specifically said ALL "sexual conduct outside marriage" is evil and governments have the right to discourage that "evil". That is really broad.
He just skipped quite a few places on the "First they came for the _____" list.
As awful as he is, the GQP forcing Mike Johnson's Puritanical values on the rest of us is doing everyone a massive favor, because it's ripping the cover back quickly to show what's underneath. I actually appreciate his hubris and audacity, because the enablers love to say that these kind of posts are hyperbole, while Johnson's own words show that the threat is very real and represents a threat to all of us.
We're at the "they are coming for us" part of the list while there are still a lot of us left. We have to hope enough of us are listening to do something about it while we still can.