[dspillett]

I think the “[non]mainstream” just changes the word, not the concept. A cult is an organised power-based religion with few members, an organised religion is often cult with many members. Aside from scale, age, and a few superficial differences, I don't see much distinction between, for example, Catholicism and Scientology. Spiritual beliefs don't even have to come into it: some political or sociological movements and even national governments have tended towards a cultish form.

> Under this definition, for example, Catholic nuns are decidedly not a cult.

That might not be the case for all convents, and there are subsets of the church where the local community develops in a controlling manner that could be considered cult-like. Within any large organisation (and the Catholic Church can be thought of as a huge organisation) subsets can end up being cult-ish even if other parts, or the whole, do not.

[Thorrez]

>I don't see much distinction between, for example, Catholicism and Scientology.

If someone leave Scientology, they're shunned by the rest of their friends and family who are still in Scientology. Not the same for Catholocism.

https://en.wikipedia.org/wiki/Disconnection_(Scientology)

Also see these schemes:

>Under this program, Scientology operatives committed infiltration, wiretapping, and theft of documents in government offices, most notably those of the U.S. Internal Revenue Service.

https://en.wikipedia.org/wiki/Operation_Snow_White

>Operation Freakout, also known as Operation PC Freakout, was a Church of Scientology covert plan intended to have the U.S. author and journalist Paulette Cooper imprisoned or committed to a psychiatric hospital.

https://en.wikipedia.org/wiki/Operation_Freakout

[dspillett]

> If someone leave Scientology, they're shunned by the rest of their friends and family who are still in Scientology. Not the same for Catholocism.

Not officially across the whole church, at least not these days, but it certainly happens in some small subsets of the Catholic community and has happened in larger subsets in the not-to-distant past. Any large enough religion tends to develop localised sub-cults.

Stepping away from the Catholics and considering other Christian groups, it definitely happens in small-town America. While there is often some extra factor (daring to be different in some other way), there isn't always, and when there is the extra factor is usually framed as being against the religion or its deit{y|ies}. Sometimes the extra factor itself results in ostracisation from the local church community, so people end up in the same position through a different ordering of the same steps and/or different levels of voluntaryness.