Implied in your so called 'question' is the statement that any online community that you know of (I shouldn't assume you know of 0 other communities, right?), you deemed less rational than lesswrong. I would say lesswrong is substantially less rational than average, i.e. if you pick a community at random, it is typically more rational than lesswrong. You can choose any place better than average - physicsforums, gamedev.net, stackexchange, arstechnica observatory, and so on, those are all more rational than LW. But of course, implied in your question is that you won't accept this answer. The LW is rather interested in AI, and the talk about AI here is significantly less rational than talk of almost any technical topic in almost any community of people with technical interest. You would have to go to some alternative energy forums or ufo or conspiracy theorist place to find a match in terms of irrationality of the discussion of the topics of interest.

You would have no problem what so ever finding and joining a more rational place, if you were looking for one. That is why your 'question' is in fact almost purely rhetorical (or you are looking for a place that is more 'foo' than lesswrong, where you use word 'rationality' in place of 'foo').