Because many people don't evaluate evidence. They join and defend tribal positions where one side is completely right. and the other side is completely wrong.

The details of the argument don't matter. It's pure identity politics and herd affiliation.

I've been exploring some of the politics groups on FB, and the level of interaction in many groups is middle school level. There are a lot of juvenile insults, preachy testimonials to a particular view - usually one that loudly insults the other side - and a lack of interest in nuance, evidence, or curiosity.

HN may not be perfect, but you don't get many comments here that simply say "The other side sucks."

I don't know if it's even possible to move past that. A primary problem seems to be that the concept of evidence-based reasoning is completely alien and exotic to many voters. It looks very much as if they're literally not able to use their minds in that way. Instead of trying to understand an issue they repeat the same insults and cliches over and over for a quick emotional hit which satisfies them they've won the argument.

The Internet - and FB - is terrible for this, because it's much easier and quicker to type a one-sentence put down than to craft an argument.

You can try to fix this by banning flames and trolling, but then a lot of the people you're trying to persuade go elsewhere for their hit.

I have no idea what a solution would look like, or where to start looking for one.

That would require time and effort, and it would force you to actually think and reason, which is a tiring activity and costly to your body. So in other words, ain't nobody got time for that.

The tool seems to be intended for those who are already polarized and don't have much interaction with those on the other side.

exactly, in so many situations, why do we have to make things black or white? this is exactly what creates "us" vs "them".