idk. It's hard.

I try to be vocally sympathetic. Like "bro you're not dumb, there's just stuff you don't know. There's way too much stuff for anyone to know everything, we all gotta keep learning all the time. Knowledge is power and I want you to be as powerful as possible. And when you tell me there's a gap in my knowledge I'll listen to you."

A lot of it comes down to the person, though. Folks have to be in the right mindset to take critiques in good faith and trust that you're being genuine.

You can also try to be like "Hey sib, so, I get what you're saying and I know this book/article/paper that talks about that, and I think you'd find it really interesting because it talks about what you're saying from a different perspective. Even if you don't agree with it you can use it to sharpen up your arguments and get a better understanding of what your opponents think"