What are some good discussions of "ideology" from a rationalist perspective? E.g., what it is, what causes people to have them, what's the best way to fight harmful ideologies, how to prevent harmful ideologies from forming in one's own social movement, etc. From what I've been able to find myself, it seems to be a rather neglected topic on LW:
I'd also be interested in good discussions of it from outside the rationalist community.
I have always understood this to be a consequence of the Politics is the Mindkiller custom. The most relevant pieces outside the Craft and the Community on LessWrong are Raemon's The Relationship Between the Village and the Mission, and The Schelling Choice is Rabbit, not Stag.
I can think of a couple relevant-but-not-specific areas outside the rationalist community:
If you want to explore the community more, I recommend reading the Library, checking recent Curated posts, seeing if there are any meetups in your area, and checking out the Getting Started section of the LessWrong FAQ.
The Open Thread sequence is here.