@Scmbradley Honestly I'm not convinced that it's so inevitable. There seem to be a few specific conditions that causes this to happen (not all deliberate), and there are also plenty of cases and circumstances where it goes fine but those don't tend to stick in people's minds.

I think the view that "internet discussions will inevitably turn bad" is kind of dangerous, actually, because it's a demotivator for improving our collective social spaces, essentially the equivalent of political nihilism.