Theism is often a default test of irrationality on Less Wrong, but I propose that global warming denial would make a much better candidate.
Theism is a symptom of excess compartmentalisation, of not realising that absence of evidence is evidence of absence, of belief in belief, of privileging the hypothesis, and similar failings. But these are not intrinsically huge problems. Indeed, someone with a mild case of theism can have the same anticipations as someone without, and update their evidence in the same way. If they have moved their belief beyond refutation, in theory it thus fails to constrain their anticipations at all; and often this is the case in practice.
Contrast that with someone who denies the existence of anthropogenic global warming (AGW). This has all the signs of hypothesis privileging, but also reeks of fake justification, motivated skepticism, massive overconfidence (if they are truly ignorant of the facts of the debate), and simply the raising of politics above rationality. If I knew someone was a global warming skeptic, then I would expect them to be wrong in their beliefs and their anticipations, and to refuse to update when evidence worked against them. I would expect their judgement to be much more impaired than a theist's.
Of course, reverse stupidity isn't intelligence: simply because one accepts AGW, doesn't make one more rational. I work in England, in a university environment, so my acceptance of AGW is the default position and not a sign of rationality. But if someone is in a milieu that discouraged belief in AGW (one stereotype being heavily Republican areas of the US) and has risen above this, then kudos to them: their acceptance of AGW is indeed a sign of rationality.
Well, it all depends on why it was downvoted. If it was a question of style and tone, I'll take that on board and take more care. If they felt the argument was incorrect, that's also relevant. Since I can't estimate how many downvoted for this reason, I'll use the critiques in the comment section as information.
But there's a bit too many downvotes for that. Downvoting from -6 to -7 is generally a sign that you really, really disliked the post (and the comment section didn't show such dislike). I can think of two possible reasons that can explain this level of dislike: maybe many see the post as troll bait/tribal, or maybe there are a few on LW who actually disbelieve AGW. In the first case, I apologise, and should have made it more clear that one of my points was that we shouldn't abandon stating the rational AGW position simply because it's tribal and attracts trolls. In the second case, it's worrying for the less wrong community.
Or that you're a believer in the "vote without reference to existing score" school of thought on karma, which some LWers are.