On your last point: This is what I fear most as well, a permanent radicalization of this individual.
One important principle in management is that you must be extremely careful NEVER to humiliate someone in even the slightest way in front of audience (any meeting >3 people by my book). The mere suggestion that "something didn't go well" can trigger extremely hurt feelings, defensiveness, and antipathy depending on the size of the audience.
Well on the internet, everything occurs in front of potentially infinitely large audience. To admit that you are wrong is to endure humiliation before the whole world. To deal with this, people dig in their heals, and claim that "I was always right, and those who disagree with me are not only wrong and stupid, but evil to the highest degree."
It's heartbreaking watching watching the far left stab their nearest ideological neighbors and most important allies.