> radical polarization and is not healthy
agree with you on this, it is not healthy if the unit of analysis for health is society as a whole, which I believe is what you mean.
> There's a difference between subscribing to a particular viewpoint versus outright rage against the other 'camp'.
not really - I think it is only in a matter of degree!
> It fractures countries and allows for populist opportunists to fester.
democracies might just inevitably do that. If we observe democratic societies outside our own Western milieu we will observe political factions battling on the streets as much as the ballot box, or even in Parliament, as in former times we saw in South Korean and Taiwan.
What we are seeing today might just be the next stage in the evolution of democracy - this is what it looks like when we democratise mass communication, enabling not only freedom of speech but dispersing the power to amplify that speech to a much greater number of people so that many more alternative narratives can propagate and cohere. This dispersal is in itself arguably a characteristic of democratic systems.