You just don't talk about it with them. You can't change the mind of someone who doesn't care what's real. The problem comes down to consequences. He can run h

You just don't talk about it with them. You can't change the mind of someone who doesn't care what's real. The problem comes down to consequences. He can run his mouth and basically second-hand-make-up how he says reality is, and he gets to enjoy the benefits of that, whatever those may be (e.g. being able to pretend he's smarter and more moral than he is). But he suffers no costs for it. In fact, he imposes all the costs on you - it's bothering you enough you're posting on the internet about how much mental and emotional effort you're spending arguing with him. This is why there should be way more of people putting their money where their mouths are, or else being called cowards. Wagers should become commonplace - skin in the game. E.g. if you're talking about a point of law, that's easy to get an objective answer on. Agree with him that you'll pick a lawyer at random, and put the question to them. The loser has to either pay $1 and admit they were wrong publicly (plus the lawyer's fee), or pay $10k if they refuse to admit it even after that (or held on trust for a charity or whatever). And be sure to get it in writing so the weasel can't squirm out of it.