Langenscheid PC Bibiothek

I haven't found a really good translation yet, especially not in one word, but here are a few possibilities to think about, and maybe bounce other ideas off of:

[increasingly] polarized [the [two] [camps | sides ] ]...

exacerbated [each other's [ actions | opinions | ... ] ]

[increasingly] drove each other to [ further and further ] extremes...

a vicious cycle of mounting [extremism | extremist [actions | ...]

It also reminds me of a "positive feedback loop" (not a translation possibility here) from audio electronics--this is what happens when you put the microphone too close to the speaker and it makes a screeching noise. Possibly a synonym or paraphrase of a positive feedback loop might lead to a solution, if we get lucky.