I don't know if any amount of internet censorship can ever stop sects from forming. You have to realize that "drinking the kool aid" is an idiom that long predates the internet going mainstream [0]. You can try to push these people off of mainstream platforms, but what will that accomplish? Ultimately, someone will create an easy to use darknet chat platform, and the more radicalized people will use that. In some ways, it's best if we can shine some daylight at the neo nazis. At least then we have some idea who they are and what they are planning.
What we had more recently was a kind of social media conveyor belt and sieve system that found, nudged and filtered people into a specific direction until there were enough deluded/lunatic/trolls/whatever you want to call them citizens from across the country willing to storm the capitol building.
Your darknet chat room just doesn't have that reach, potentially it has the reach to organise domestic terrorism in terms of bombings or something similar, but you'd never get a group of people so self assured in their bubble of reality that they'd willingly assault the capitol building.
While this sounds reasonable, it is not at all clear that it is truly the case.
One day I walk in the house and see my mother crying, watching TV, and pictures of a lot of people laying down. My mother was NOT a crier, so this scared the crap out of me as a child, and is probably why I remember it so starkly today. At some point years later I came to learn what was actually going on that day. (My mother was also not an explainer.)
I wince when I hear the phrase used casually. But of course, people have largely forgotten the deeply dark connotations it has.
Anyway, even though we can’t ensure radicalized sects don’t form, simply ignoring them as the post above mine suggested, is not any kind of solution. As we’ve seen, such groups won’t necessarily be satisfied to just talk among themselves.
The events of Jan 6 show that leaves a rather huge problem unsolved.