This article is a deliberate meta-troll. To be successful I need your trolling cooperation. Now hear me out.
In The Strangest Thing An AI Could Tell You Eliezer talks about asognostics, who have one of their arm paralyzed, and what's most interesting are in absolute denial of this - in spite of overwhelming evidence that their arm is paralyzed they will just come with new and new rationalizations proving it's not.
Doesn't it sound like someone else we know? Yes, religious people! In spite of heaps of empirical evidence against existence of their particular flavour of the supernatural, internal inconsistency of their beliefs, and perfectly plausible alternative explanations being well known, something between 90% and 98% of humans believe in the supernatural world, and is in a state of absolute denial not too dissimilar to one of asognostics. Perhaps as many as billions of people in history have even been willing to die for their absurd beliefs.
We are mostly atheists here - we happen not to share this particular delusion. But please consider an outside view for a moment - how likely is it that unlike almost everyone else we don't have any other such delusions, for which we're in absolute denial of truth in spite of mounting heaps of evidence?
If the delusion is of the kind that all of us share it, we won't be able to find it without building an AI. We might have some of those - it's not too unlikely as we're a small and self-selected group.
What I want you to do is try to trigger absolute denial macro in your fellow rationalists! Is there anything that you consider proven beyond any possibility of doubt by both empirical evidence and pure logic, and yet saying it triggers automatic stream of rationalizations in other people? Yes, I pretty much ask you to troll, but it's a good kind of trolling, and I cannot think of any other way to find our delusions.
More of an empirical evidence thing, with some logic supporting it: For the vast majority of people, their fat percentage says nothing about their health or how well they're living their lives. The cultural opposition to fatness is status-driven, and should be viewed as signaling gone out of control.
The demand for leanness has made people's lives (including their health) generally worse rather than better.
This looks like evidence against that to me. See also this. (All that publicity for anorexic models is still a Bad Thing, but “opposition to fatness” needn't mean endorsement of emaciation; the latter is signalling gone out of control.)
ETA: FWIW, all other things being equal I feel better (e.g. more stamina) when I'm slimmer; YMMV.