Perhaps just one or two, if we judge from Twitter. That's what makes it such a powerful radicalizing force. I recall, years ago, the difficulty in getting Twitter to promptly remove pro-ISIS twitter accounts. One voice, repeating itself enough, looks similar to a crowd. The icons aren't enough, it just looks like a lot of people, and that's how we develop instinctual guesses about this.
I think there's a lot of room for exploring media where individuality is preserved a bit more, if only because it's more human. I don't think podcasts, for instance, radicalize much – but long-form, frequent, one-way communication is, again, unnatural and distorting. Voice is better than text, which is better than an ocean of only slightly differentiated text blobs.
Communities live and die by the ability for one person to have, unchallenged and present in the space, complete nonsense. I recently had an interaction where someone said it wasn't logically coherent for me not to like a thing because I saw it, and thought it was bad, even though they didn't think it was bad. Wrap your head around this. Like it's a logical contradiction to have different preferences.
As an aside, they also think I didn't have a firm grasp on the subject, and was misrepresenting it – but they think even my misunderstood description's not so bad. Isn't that the end of it, it's just a matter of different values. But they'll never let you just say, we disagree. You'll get pings back about it for eternity.
These people live in a different reality. It's impossible to have a meaningful conversation with them, although it's possible to have a polite conversation. But why spend the time, when you could have nice conversations elsewhere, or, frankly, just sit quietly, which sounds nicer than the weird gaslighting of people who insist people endorse their preferences.
But this is the bear-trap of any community. Someone will have a conversation, perhaps totally normal, and then, boom, out of nowhere, someone defends Kim Jong-Un as being a reformer, so I'm nopeing out of there. Like, I disagree extremely strong, obviously, but man, there's only so many hours in a day, ya know? Who cares if it's just one insane voice in a dense, high-value conversation – that one voice, unchallenged, lowers quality so much that I just choose not to participate. I'm not sure there's a sanity-preserving second option.
Online conversation is difficult. And it's getting harder. But I think part of it is, we all assumed we could write our way through the problems. I just don't think that's working, when text creates the appearance and reality of an orthodoxy even if it's just one person (perhaps even bots or paid Chinese internet commenters).