I actually was in a situation where I had such a debate during Covid with someone I was in school with. I tried to take time to argue.
He would show some numbers and make completely wrong conclusions. There was no way I could get him to try to listen to me. Whereas back at school, he was never arguing with me about maths given that he had bad grades and I didn't.
So somehow I really feel like there is this "authority" thing missing. Now that he is an adult, he feels like his opinion about everything is valid.
Your comment makes me wonder if a large part of what's driving this is the proliferation of so many disparate (sub)cultures, and specifically the brain drain away from the subcultures that had been the traditional societal defaults.
When you were at school, you were both part of the same social hierarchy. On the topic of math proficiency (general smartness, really), it was easy for him to perform a mental check and see that you were above him in that aspect (even if he was above you in other aspects), and so he should listen to you.
But then you probably went your own way, essentially getting out of his way with him continuing to advance in that traditional subculture. So now he feels he's earned being considered closer to the top of the hierarchy, even though it's no longer a pan-society hierarchy!
And then he also cannot understand where to slot you into his mental model. So you just get written off as an outside attacking force to be opposed.
This also explains why they continue calling themselves "conservatives" despite gleefully working to destroy our institutions and standing in the world - what they want "conserved" is their perceived prominence of the subcultures they bought into.
That's an interesting point of view: in a way he "doesn't know me anymore", so why would he trust me? And he has to trust me because if he doesn't understand why I am better in this specific topic (maths), then the only thing left is his belief...
I once heard flat-earthers in a train. One was saying "It's like school, e.g. physics: they purposely make it such that we don't understand it to confuse us. Because we're not worse than anybody else, so we should understand, right? If nobody understands, that's because they bullshit us!". I really wanted to say "counter-example: I could understand physics at school :-)".
Thing is that people are entitled to have different opinions and we can argue about those all day. But people are not entitled to different facts, and if someone pretends 2+2=5, then there's very little arguing about that. It's not that I'm too tired to argue, but if someone is so far out of the common ground, there's no basis on which it makes sense to argue because they'll just declare all of your premises void and "win".
And perhaps a broader point is: "Facts are simply opinions we generally agree upon."
At its best, "Science" doesn't claim the force between two objects is proportional to the product of their masses. It merely observes that this has been the case in all known, well-documented instances, and attempts to find exceptions have failed, so that this "law" is valid and reliable, and expected to remain so forever.
We use the term "fact" very casually, and eagerly. "The Dow is up 20% year-over-year, unemployment is under 4%, and the dollar is strong. The economy is strong. That's a fact!" Not only is that not a fact, it's not even a fact that unemployment is under 4%. That's (presumably...) just the U3 number as published by the Department of Labor.
My point is: the best "facts" still require a certain amount faith in the data sources around us. That's fine. I don't wish to visit every country on Earth to ensure that it exists, and observe the weighing of the Kilogram in Paris. (I mean, unless I can take time to sightsee a bit.)
There has been a genuine breakdown in that faith in authority in US culture. Maybe Ukraine attacked Russia first. Maybe poor people are inherently lazier than rich people. Maybe the Earth is flat.
I believe this breakdown has been intentionally orchestrated and groomed and fed by nefarious people like Rupert Murdoch, but that's just an opinion. Based on things I like to call "facts".
