The principle alleged by you is that it is cult like behavior to prevent reading.
No, I didn't make it a principle that all prohibitions are cult-like.
For example, if the SSPX said not to read a book that was notoriously anti-Christian, I wouldn't have a problem with that.
I have showed that the Church Herself has prevented reading.
Which shows your principle: what the SSPX does it does with the authority of the Church.
I explained my reason this is not binding before: What the SSPX is saying about its priests is the same thing conciliarists could have said about their priests in the 60s, when they were selling out. Someone uses some rhetoric they regard as intemperate, so then they use that as a pretext to keep people from getting information that doesn't come from SSPX sources.
That's cult-like. A small group inside the Church, using its non-existent authority to control discussions about its theological positions.