Earlier quoted context omitted.
I personally use the meta-conversational move a lot, and it usually turns heated political discussions into more thoughtful philosophy discussions. I think because most people don't have such strong identity based beliefs around questions like "how can we know if something is right/true/good/bad, what does that mean?"
The meta-conversation technique blew up for me once. A buddy and I got into it and I went in that direction of how do we know if something is good or bad, right or wrong, and it had him feeling incredibly frustrated and distraught, questioning whether his friends have fundamentally different values than he does. I recognized in that moment he seemed very emotionally vulnerable and so I switched out of my head explora…
I've seen this state called different things, like "Exiles" in IFS therapy, "below the line", "tilted", "triggering painful spots", I usually call it "defensive".
(Aside... a thing I've learned is not to ask if someone is feeling defensive (if they are, they'll say no). Instead I think the better move is to ask if they feel like I'm not listening, or not understanding their position. This lines up with the internal thoughts of feeling defensive.)
All this to say, rational conversation is possible when two people are in a rational state but there are other states of being.
(Aside.. I find that rational communication techniques like NVC are actually devilishly hard to put into practice all the time because they go out the window when we get tilted.)
(Aside... EFT couples therapy is designed around communication in an emotionally vulnerable state as opposed to rational, and supposedly has pretty good empirical results)