I don't think the argument is that their sexual practices inherently make them part of a cult. Rather, the argument is that it's very common for cults to include communal sexual practices that fall outside typical social norms.

Common signifiers of cults include:

1. Apocalyptic world view.

2. Charismatic and/or exploitative leader.

3. Insularity.

4. Esoteric jargon.

5. Lack of transparency or accountability (often about finances or governance).

6. Communal living arrangements.

7. Sexual mores outside social norms, especially around the leader.

8. Schismatic offshoots.

9. Outsized appeal and/or outreach to the socially vulnerable.

Rationalism checks most of these boxes.