Voted up.

if you have to choose between fitting in with your group etc and believing the truth, you should shun the truth.

I think many people develop a rough map of other people's beliefs, to the extent that they avoid saying things that would compromise fitting in the group they're in. Speaking of which:

irrationalists free-ride on the real-world achievements of rationalists

Trying to get to level 4 are we? (Clearly I'm not ;)) Conversely, you could argue that "irrationalists" are better at getting things done due to group leverage and rationalists free-ride of those achievements.