As many people have noted, arguing on the Internet is a spectator sport. You don't need to convince your opponent, but by steel manning his arguments and addressing them, you have a greater chance of convincing the audience.
I used to believe this and found myself frequently arguing for any audience that might happen by versus trying to convince my interlocutor.
But, I have come to believe that, in the "emotional" domains that GP mentions, the dynamic is largely the same for any audience as well.
That is, you're not winning them over either if their beliefs are already set and were also never based on reason in the first place.
Yet being that open can be very socially costly, as it was for me. If I'd heard steel man arguments from opponents while still closed to inconvenient truths, then I'd just have accept them without critical thought. And any attacks on that steel man would have been dismissed with whatever was convenient. It devolves into Rube Goldberg levels of mental hoop jumping to stay in that mindset. Though if the alternative is strained relationships or losing ones church community then it becomes second nature, even unconscious.
It's also quite dangerous if you're attached to your beliefs. I rarely walk away from steel manning an argument without being persuaded to some degree into a compromise position.
I try to ask myself: "would I make this argument privately?" If not, I probably won't reply publicly. (I often fail to make the right choice, however.)
I mean, outside of some niche debate club blogs subcultures, who does thus?
When there's a presidential debate, does the debater first improve the other guy's argument that he's corrupt before denying it?