The main way I've seen people turn ideologically crazy

I’ve seen people around me and in the general public turn ideologically crazy at a higher rate than I expected to in my adult life. I lost one friend to a cult. Others became so brittle that they can barely interact with normal people without freaking out over tiny disagreements. Others have just become very ideologically single-minded and attached to very specific (and in my opinion not very convincing) accounts of the world. These people’s backgrounds, and the ideologies they went crazy over, were all wildly different from each other. But underlying all of them is a single really bad dynamic that I think is actually easy to identify and stop. The dynamic goes like this:

1. You develop an extremist idea.

2. You bump into a lot of people who disagree with the idea.

3. Almost every single person who disagrees with you comes off as wildly misinformed about basic facts about the world, and have pretty horrible background moral intuitions about simple ethical questions. Their disagreements are also very visible entirely rooted in their pre-existing social identity.

4. You conclude that the vast majority of critics of your extremist idea are really wildly misinformed, somewhat cruel or uncaring, and mostly hate your idea for pre-existing social reasons.

5. This updates you to think that your idea is probably more correct.

My claim here is that the only thing wrong here, the thing that really messes people up, is that last step where you update in favor of your idea.

I’m not against extremist ideas on principle. I have my own, the main one being that animal welfare is a much larger urgent catastrophe than most people believe. But I think extremist ideas should come with a few warning labels.

The main danger with believing an extremist idea is that it’s very very easy to be negatively polarized by a ton of bad conversations with normal people about it, until you feel like the whole rest of the world is crazy and asleep. The reason it’s so easy is that most people are in fact “asleep” about most things most of the time, not super thoughtful in how they develop beliefs, and really only have expertise in a few areas often related to their jobs.

Suppose you become politically radicalized and become a Marxist. You get convinced that the labor theory of value is correct. You learn all about the pantheon of Marxist ...