I can't even formulate a "rationalist" argument against that wisdom, besides some vague guesses that principles of social organization and grand-scale value conflict like farmers vs. foragers - what LW likes to dismiss as "politics" - might stay important after we handle FAI, death or scarcity.

Trying to rationalize something like this is much worse in the long run. Intentionally acting irrationally is much better than acting the same way, but believing it to be rational.

This advice is more useful on the meta-level of having a community norm of accepting people who do this. (Do we already have such a norm? I know that I act as if such a norm exists, but I am unsure if others do.) The good thing about Less Wrongers is that you can get them to adopt such a norm just by explaining why it would be useful.