Well, that's actually progress for you. Before you kept claiming that erroneous stuff was simply not part of the Magisterium. Indeed, there are non-infallible things in the Magisterium. But this isn't about nitpicking the limits of infallibility. We're not talking about a couple of offhand comments in an Encyclical letter that can be respectfully questioned ... but rather about a wholesale corruption of the Magisterium and the replacement of Catholic truth with a new non-Catholic theological system. R&R posits that the Magisterium has become so thoroughly corrupt, and the Church's Universal Discipline so defective, that Catholics cannot in good conscience go to that Mass or submit to the Magisterium without corrupting the faith. So R&R lose the forest (of indefectibility) for the trees (of infallibility). If Catholics have to reject the Magisterium and refuse to attend the Mass, if the Magisterium and Mass have become dangers to the faith, then the Magisterium and Universal Discipline of the Church would have defected.
On the one hand you have a number of dogmatic sedevacantists who exaggerate the scope of infallibility, right down to "negative infallibility" Nado who basically was on record saying that anything the Church has failed to condemn must be true, and others who claim that any minor book with an imprimatur from a local ordinary must be considered de fide for all intents and purposes. On the other you have the R&R who claim that the Magisterium and Universal Discipline of the Church can lead souls to hell. So the dogmatic sedes overreact to the R&R minimalization of infallibility (basically limiting it to solemn definitions) by exaggerating the scope of infallibility in the other direction.
You have an ambiguous idea of what the Magisterium is.
Per V1, we know that there can be no new doctrines and if in fact anyone, literally anyone - even an angel from heaven - teaches any new doctrines, we are not permitted to accept or believe them - period. The whole of V2's NO is a new doctrine, ergo, we are bound to reject it. No "magisterium sifting" or nitpicking involved. The Church prior to V2 already taught since the time of the Apostles that we are to reject new doctrines. Simple.
The indisputable fact is that the NO doctrines of V2 are new doctrines, the only thing guaranteed by the Church in regards to the new, NO doctrines, is that they are most certainly *not* protected from error by the Holy Ghost, as such, they are not binding on the faithful and are in fact to be completely avoided by the faithful. Again, simple.
The sedewhateverists, for whatever reason, profess these doctrines are supposed to be infallible because they are taught by the hierarchy whom they call "the Church" or "the magisterium", but since even they know that these new doctrines are in fact heresies, they say falsely the pope lost his office because popes are not permitted to teach heresies, they further say that those who disagree with their false idea of what the Church and magisterium is are either wrong or heretics. All V1 states is infallibility is not promised to make known new doctrines.
I think this explains it nicely - from an old Catholic Dictionary:
It only remains to determine the subject-matter to which this infallibility extends. Clearly neither pope nor Church can put forth new dogmas for acceptance. The faith has been “once delivered to the saints”. The [First] Vatican Council lays down this point with great lucidity. “The Holy Ghost was not promised to the successors of Peter in order that, through His revelation, they might manifest new doctrine, but in order that, through his assistance, the successors of Peter might religiously guard and faithfully expound the revelation handed down by the Apostles, or the deposit of faith.”The Church has no inspirations, She cannot receive fresh revelations to be imposed on the belief of the faithful. Her office is confined to expounding the original revelation, to the condemnation of new error and the drawing out of ancient truth, which may not, as yet, have been perfectly understood by the faithful. When the Church defines an article of faith, we are bound to confess that this doctrine is true and to be accepted without doubt, next, that the doctrine was revealed to the Apostles and preserved in the Deposit of Faith, as contained in Scripture and Tradition. So what we have are Magisterial teachings that infallibility is not promised to any new doctrines and that we are to reject new doctrines, but we have a hierarchy preaching new doctrines. For our part, we are expected to listen to the Magisterial teachings of the Church - if we do that, then we reject the new doctrines taught by the hierarchy. That is not sifting the magisterium, that is simply remaining faithful to the magisterium.