What do you think a person like me or you can do to maintain our ability to critically think?

There are probably some specific practices one could follow, but I'm guessing one would be to stop paying attention to the incredible retardation that appears to be overtaking our species. I'm not doing it, but I think isolating oneself into a subset of reality might allow some critical thinking.

As for your friend, what specifically is he angry about? Therapists have techniques to draw out answers from people with anger or other problem emotions. I don't think I can describe in a comment how to go about that without potentially 'setting him off' in an angry episode. You kind of have to elicit some of that emotion to access the reason he's holding on to the anger.

You could just ask why he's so angry. To maintain rapport, assuming you have it, repeat whatever he says back to him, as follows.

"Dudebro, I hear you saying you're angry because [insert the exact words he used here]. Is that right?"

It's kind of a delicate process to access someones highly emotional state. I don't think I'm able to tell you in a comment how to help your friend be less angry and make better decisions. I guess being as sympathetic as you can be, while evaluating his answers and non-verbal responses might be an approach.