To riff off a Douglas Adams quote: "In the beginning the [internet] was created. This had made many people very angry and has been widely regarded as a bad move."
Much has been said about the anger that the rode shotgun with the internet's arrival - anonymity has been blamed, as has the lack of body language, etc. - but there's one explanation that I haven't seen: I call it "generosity of nuance."
The idea is that many statements are alternately true and not true depending on what level of nuance you go into. Arguments involving this tend to look like this:
|Person A:||X is true|
|Person B:||Read Y, it shows that X only looks true if you don't know anything about it|
|Person C:||You ignoramus, Y was debunked by Z|
And so on... You've seen it thousands of times.
Scott Adams (who, for the record, says a lot of other things that I disagree with) came up with a great metaphor: "One Screen, Two Movies." It's where, depending on what political camp they're in, people will arrive at completely different and incompatible interpretations of a given objective event.
It captures the current gestalt well, I think, and raises the question of "how?" Certainly it's multifactorial, but I propose that differing generosity of nuance explains a lot of it.
For an example, let's take the topic of taxation.
At level one - the lowest amount of nuance - you have money, and then someone comes along and demands some of it, and if you persistently refuse to give it to them eventually things will escalate until someone with a gun (i.e. a police officer) arrives and threatens violence. That absolutely fits the definition of a shakedown. So at level one "taxation is theft" is a completely valid take.
Level two adds some nuance: that collective action is sometimes the only reasonable course of action (e.g. firefighting) and taxation is an unpleasant but successful way of funding such things. And that the aforementioned person with a gun is constrained by the rule of law, and that the taxation was willingly imposed (via democracy, where applicable) on ourselves.
You can easily find a level three, and four, and so on - branching into deeper and deeper levels of nuance, each reversing the arrow of truth. You can bring in essays, studies, and then the controversies surrounding the people that wrote those essays and studies, and so on until you arrive at such levels of esotericity that your arguments can be dismissed just on that basis.
The critical feature of this, though, is that it's natural for people stop at the level that suits them. So all that's required for the world to match your worldview is to allocate the appropriate level of nuance to each topic.
This might seem the same as looking for sources that agree with you, but it's a better tool for self-deception than that. Because nuance in any topic requires concessions to the "other side" - that's almost the definition of nuance in politicized topics - it means that you can read from opposing sources and arguments and still be able "watch your own movie."
A way to detect this (in yourself, or in online discussions) is to see how "ragged" the level of nuance is. In a perfect world, all points in a discussion should be at a similar level, descending gradually as a topic is explored. The opposite - where people are jumping up and down levels to prop up various points - is a pretty good indication that the discussion is going to generate more heat than light.
And if you could point out someone's over- or under-generosity of nuance, would that point a discussion in a better direction? By itself, I doubt it - I think there's much more that's required to solve online angst - but perhaps being aware of it could be part of making the online world less furious.