> On top of all that the forum is skittish about embracing controversial political topics in general, because many people would prefer to just talk about tech. Why wouldn't HN users flag some Michael Moore content to oblivion? What is wrong with this?
There's nothing necessarily wrong with the flagging itself (well, except in this case I believe a lack of awareness of the content of that documentary likely contributes to ongoing destruction of the earth's ecosystem)...but there is a problem where the moderator of HN claims that what you say above is outright false. Purely a misperception on your part.
Another way I can see it being harmful: a never-discussed here (or anywhere else that I know of) topic that I believe may be a key issue with the growing polarization in the world (in turn increasing danger across multiple dimensions), is that there seems to be certain topics that render the human mind unable to sustain consciousness and rational, unbiased thought. Of course Reddit and Facebook are full of this sort of behavior, but there is no shortage of it here on HN either. If solutions to existential threats like climate change require public consensus (do they not?), and even we here on HN are unable to behave in a conscious, logical manner (or even try), then how do we expect the general public to do so? And if no one here is even willing to consider the potential importance of this idea, then those same people shouldn't be too surprised if people like me (and I'm far from unique in this respect) have about as much respect for them as they have for Trump supporters, and roll our eyes at the low-dimensional thinking behind climate change hysteria. If it was really that important to people as intelligent as HN'ers, they should be willing to think - or at the very least, consider the notion of thinking.
As for how this general phenomenon may be dangerous: as a mental experiment, let's assume that it is a very real phenomenon, that does occur in objective physical shared reality. That's bad enough. But now imagine if one or more powerful entities were able to realize that certain things are virtually guaranteed to sink humans into subconscious, unthinking, tribal, non-cooperative behaviour. Could this knowledge be used for nefarious means, and what might the techniques look like? Now, look around the modern world - do we see any new (in the last decade or so) phenomena that have become quite common that may plausibly be invocations of these techniques, to achieve certain goals? Might that perhaps go a little ways to explain the inconceivably irrational behaviour of people on certain topics?