As a matter of interest, would people define Yevon (in FFX, not New Yevon from X-2) as a religion or a cult?
On a quick Google search, BBC defines a cult as:
- Uses psychological coercion to recruit, indoctrinate and retain members: there's plenty of psychological nonsense going on, though I can't say they seem to coerce much. Any pressure for Tidus to follow them comes from societal norms rather than Yevon itself and allowing him to stroll around the cloisters is based on being sworn to protect Yuna rather than being sworn into Yevon itself.
- Forms an elitist society: I'd say yes, since in X Yevon also acts as a government and only followers are welcome and afforded the protection and care that comes with it, while non-believers are essentially banished to the sea.
- Founder leader is self-appointed, dogmatic, messianic, charismatic and unaccountable: Taking Mika as leader - I'm not too sure how they're appointed, but he's supposed to be dead and decided the world needed him, so the definition of "self-appointed" is close enough. Dogmatic, sure, everyone is expected to believe that Sin will disappear when their own sins are atoned. Though most/all religions are dogmatic as well. Messianic - somewhat. Charismatic - not particularly. Unaccountable - definitely (until Yuna and co make him accountable anyway!)
- Believes the 'end justifies the means' in raising funds and recruitment - The end justifying the means is quite a common theme with Yevon in the game. An obvious example is the use of machina despite it being otherwise banned and considered unholy, justified because it's used to protect Yevon's interests. However they don't really need to recruit since it's so ingrained in society, as for raising funds I don't know. Tricky one - the end justifying the means is extremely familiar in this game, but it's difficult to pigeon-hole into the categories of recruitment and fund raising.
- Its wealth does not benefit its members or society - Not too sure. It's not too clear what's funded by them (is Luca?) but there is a sense of you being on your own, and it's the Al Bhed who have set up resting places and shops to support you on your journey. So perhaps it doesn't.
So..... they have a lot of cultish properties. I'd say by my reckoning they're about 50-60% cult but not a "complete blatant cult" or anything. So there's that to take into consideration as well: being anti-cult is a bit more understandable than anti-religion or anti-god, and to be fair it's the most cult-like sides of Yevon that are picked apart the most by the game.