Jargon is a tool, sometimes inevitable—for example math is full of jargon.
But it can also be abused strategically. Renaming things needlessly, to make it more difficult to communicate with the outsiders. Renaming things needlessly, to make members believe that the idea originated in the cult (as opposed to being taken from outside and renamed), so they can’t research the idea independently. Renaming things needlessly, to get rid of associations: for example many would agree that hurting people is wrong, but they have no strong opinion on whether frobnicating people is wrong, so you just need to tell them that what seems like hurting people is actually frobnicating, and then they will be more okay with that.
You have a point but this requires more nuance.
Jargon is a tool, sometimes inevitable—for example math is full of jargon.
But it can also be abused strategically. Renaming things needlessly, to make it more difficult to communicate with the outsiders. Renaming things needlessly, to make members believe that the idea originated in the cult (as opposed to being taken from outside and renamed), so they can’t research the idea independently. Renaming things needlessly, to get rid of associations: for example many would agree that hurting people is wrong, but they have no strong opinion on whether frobnicating people is wrong, so you just need to tell them that what seems like hurting people is actually frobnicating, and then they will be more okay with that.