The podcast Behind the Bastards described Rationalism not as a cult but as the fertile soil which is perfect for growing cults, leading to the development of cults like the Zizians (who both the Rationalists and Zizians are at pains to emphasize their mutual hostility to one another, but if you're not part of either movement, it's pretty clear how Rationalism can lead to something like the Zizians).
I don't think that podcast has very in-depth observations. It's just another iteration of east coast culture media people who used to be on Twitter a lot, isn't it?
> the fertile soil which is perfect for growing cults
This is true but it's not rationalism, it's just that they're from Berkeley. As far as I can tell if you live in Berkeley you just end up joining a cult.
I lived in Berkeley for a decade and there weren't many people I would say were in a cult. It's actually quite the opposite. There's way more willingness to be weird and do your own thing there.
Most of the rationalists I met in the Bay Area moved there specifically to be closer to the community.