The Soviet Communists did this to themselves too in the 20s and 30s once they had defeated the "Whites". All in the name of ideological purity. It will only get worse. Denouncements. Political violence. Ostracism. Death. It will be interesting to see how this progresses. The stuff I read about college campuses is chilling. The lack of respect for free speech is especially quite troubling. Having read so much European history, I know where this can go and I do wonder if the extreme ideological militants have read their history too. Or even care if they have.
Don't they need to actually win first? Eating your allies for ideological purity reasons is part of a logical progression that sort of makes sense if you cross your eyes and squint while you consider it, and has historical examples as you point out.
Doing it while the other side has control over all three branches of government and most of the state governments is nuts. More baffling still is the appearance that the driving forces behind the auto-cannibalism appear to originate in the university system. (Maybe not, considering how thoroughly the Left controls the universities, now) One of the things I assume about college students and professors is that they are smart. My belief in that is getting shakier by the day.
Perhaps the problem is the fetishization of intelligence over wisdom. Maybe they are smart, but just incredibly unwise.