One issue is that if you base your self-esteem on your rationality, that might make it more difficult to notice flaws in your rationality, for the same reasons as basing self-esteem on being a Nazi might've made it more difficult for historical Nazis to notice the issues. Hence the idea of keeping identity small, not including important things in it, to avoid that particular cause of misperceiving them.

See Cached Selves for more details. There does seem to be an important difference between the usual ideologies and technical subjects, in that ideologies allow much more wiggle room, which might be at the heart of the problem, see Ethnic Tension And Meaningless Arguments. Sidestepping that sort of vagueness by making sure a few key ideas remain clear is also the approach explored in Yudkowsky's How To Actually Change Your Mind, for example see The Scales of Justice, the Notebook of Rationality and Human Evil and Muddled Thinking.