No, I mean that a major part of LW culture appears to be an irrational terror of believing things that aren't "true"

Irrational?

If you refuse to accept false beliefs that present themselves as useful, and refuse to tolerate any knowing self-deception in yourself, and you pursue this path as far as you can push it, and you have the intelligence and background knowledge to push it far enough, then uncompromising truth-seeking pays a dividend.

If you decide that some false beliefs are useful, you don't get to take even the first steps, and you never find out what would have happened if you had pursued truth without compromise.

Perhaps you find that a false belief on this subject is more convenient, though...?

(I need to write up a canonical article on "No, we are not interested in convenient self-deceptions that promise short-term round-one instrumental benefits, we are interested in discovering the dividend of pushing epistemic truthseeking as far as we can take it", since it's a cached thought deep wisdom Dark Side Epistemology thingy that a lot of newcomers seem to regurgitate.)