This seems like an awfully uncharitable and cherry-picked treatment of a community of well-intentioned and occasionally eccentric disagreeable online nerds. You're effectively just noticing that a community that actively aims to overcome bias is not free from bias itself, but no one within that community would ever deny that.
That's what can make the rationalist movement feel more like a religious cult and less like a bunch of eccentrics. As an outsider looking in, it seems like the entire movement is filled with just accepting priors with very little evidence for why those priors should be accepted.