I think your language, even in the title, indicates the problem with the question, and why, while I appreciate the goals, purposes, and actions of the lesswrong crowd, I wouldn't consider... um, "joining up."
The whole premise, as I see it, of being a rationalist is that there are particular methods to working with truth, that there is an actual truth, and a solid, singular rationality. The problem is that there is no sense in, having begun using them, declaring that you are now in charge of the truth or really have any particular access at all.
Statistical analysis doesn't prove things correct. It allows us to prove things incorrect. The assertion that whatever is left is true, is correct, typifies rationality.
But here's the thing, here's why it's called lesswrong, why the idea is to increment in favor of the truth: everyone's actually pretty rational. Some people are more wrong than others, but given the assumptions they work with, they are making rational choices.
If you are declaring people irrational, the problem is with your definition of rationality, not with them. In finding out _why_ they are rational you will find out _why_ they think differently than you.
Take atheism vs. theism. The assumption of irrationality on either party shuts down debate and lets no information traverse between the viewpoints.
But if you realize that everyone's pretty much the same, the problem you raise just _goes away_. Everyone's at a different place on the axis of rationality, no one is stupid, and there are people who are more right than you so there's not much point being annoyed with those who are less right.
So calling one's self a rationalist, to me, is either equivalent to saying "I am a human being," because all humans are somewhat rational and believe in the assertion that true things can be known (whether they say so or not), or "Other people are dumber than me and that is a part of my identity."