There are a lot of rationalists in this community. Pointing out that the entire thing is a cult attracts downvotes from people who wish to, for instance, avoid being identified with the offshoots.
No, the downvotes are because rationalism isn't a cult and people take offense to being blatantly insulted. This article is about cults that are rationalism-adjacent, it's not claiming that rationalism is itself a cult.
I agree that the term "rationalist" would appeal to many people, and the obvious need to belong to a group plays a huge role.