Let's say that 99% of the Magisterium does not meet the notes of infallibility. According to you, then, Pax, is it possible that that 75% of the remaining non-infallible Magisterium (that 99%) could go corrupt at any given time in history? I'm not asking whether you think it's probable, but whether you think it's theoretically possible.
First off, in my mind, the magisterium is an office, not a people. So when we use the term magisterium I think of teachings, which is why I distinguish between the hierarchy and the magisterium's TEACHINGS (which come from the hierarchy/clergy). So the magisterium includes encyclicals, papal bulls, speeches, the 'urbi et orbi' greeting, synod docuмents, etc.
Is it possible for the hierarchy to lose the faith? Absolutely. Church history proves this over and over. Is it possible for the ALL the hierarchy to lose the faith? No. But 99%? Yes.
Is it possible for a SOLEMN, infallible act of the magisterium to teach error? Of course not.
Is it possible for the 'ordinary' magisterium to err and propose BINDING error on the faithful? No, this has never happened and cannot.
Is it possible for the 'ordinary' magisterium to err and propose
non-binding error, as at V2? Yes.
Is it possible for the hierarchy to be infiltrated by anti-catholics and to propose non-binding error to the faithful? Yes, reality proves this.
The key issue is if a teaching is 'binding' because all teachings which are binding have been taught with apostolic authority, both infallible and non-infallible, and the magisterium can teach both kinds. A binding, authoritative teaching is OFFICIAL teaching. Anything which is non-binding is also non-authoritative, by definition and hence, not official church teaching.
Indefectibility protects the Church from being corrupted in Her OFFICIAL teachings, in Her official OFFICE of the magisterium as AUTHORITY on faith/morals. V2 was not authoritative, it was not binding and therefore we cannot consider it official church teaching because we are only required to give CONDITIONAL assent and we are ALLOWED to question it.
The hierarchy pushed their false interpretation of V2 upon the faithful, and they tried to use their PERSONAL DIOCESAN AUTHORITY as Bishops to impose V2. This authority is NOT THE SAME as the magisterial authority coming from the pope, who never imposed V2 on anyone. This is the key difference.