I am genuinely interested in how you come to this conclusion and which left wing groups you believe do this.
When dealing with the far or extreme right, they are usually easily identifiable. As soon as they start talking about segregation, ethno-states, racial superiority etc you can basically fuck them off, and remove them from the discussion, as its pretty much universally agreed this is a bad thing.
The issue with the far or extreme left is that when they portray similar ideologies to those of the far/extreme right (horseshoe theory and all that), there isn't a similar point of reference or metric where you can do the same.
This is because the far/extreme left use a playbook that even Stalin would of been proud of, to disguise what is essentially a power grab.
They position themselves as caring using words like diversity, equality etc and when those things are attained move the goalposts to introduce concepts such as equity (fairness), to continue favouriting certain groups.
They achieve this by pitching everything from the viewpoint that everyone falls into 2 categories; you're either oppressed or an oppressor, and then they take it further.
They remove any dissent, disagreement or criticism by labelling those against them as oppressors, and for everyone else create a 'us and them' situation ('if you aren't with us you're against us') to bring them into the fold, or at the least remove any objections.
If you want to see this sort of thing in action just watch the below 3 part youtube documentary on Evergreen State college
I would love to be able to say 'Only in America' or 'The Lunatics have taken over the Asylum'
but its more likely 'Coming soon, to a campus near you'
If you don't see anything in the above vid that concerns you i genuinely despair.