Left wing radicalism cannot thrive within an environment of civil, rational discourse. That is because this kind of conversation, by its very nature, forces us to examine every aspect of an issue on all sides; and this leads us to realize that solutions to big problems are always very complex, and not at all straightforward. The issue with that realization is that it conflicts with the radicals demand for the immediate upheaval of the status quo, and the replacement of it with a new and “more just” order. Things become far less certain for the zealous, enthusiastic reformer; careful, rational deliberation shuts down the case for radical political adventures.
This is why radicals seek to enflame emotions rather than identify clear arguments for policies. They incite passions over supposed social injustices instead of providing conclusive evidence for approaches that would constitute an improvement. In reality, he knows that he does not have definitive answers to these problems, and he will openly admit to his own peers that they are still learning and figuring out the best approaches. So what the Left wing radical is actually doing is demanding political power in general to be used experimentally as he figures out over time what the best solution is for every situation that society faces. He wants power carte blanche. But this is the essential characteristic of the authoritarian. And so what we see here is that radical thought naturally contains the seeds of authoritarianism.