> I assume you think you're not in these sections? And probably a lot of people in those sections say the same about your section, right?

You're saying this a lot in this thread as a sort of gotcha, but .. so what? "You are not immune to propaganda" is a meme for a reason.

> private manipulation - convincing someone of something they should not talk about with regular people because they wouldn't understand, you know - is a lot more powerful than public manipulation

The essential recruiting tactic of cults. Insider groups are definitely powerful like that. Of course, what tends in practice to happen as the group gets bigger is you get end-to-end encryption with leaky ends. The complex series of Whatapp groups of the UK conservative party was notorious for its leakiness. Not unreasoable to assume that there are "insiders" group chats everywhere. Except in financial services where there's been a serious effort to crack down on that since LIBOR.