Yeah. The problem is that this is false reasoning. It is a Catholic dogma that the Apostolic See of Rome will always "hold out". Per the IVth Council of Constantinople:
The first condition of salvation is to maintain the rule of the true faith. And since that saying of our lord Jesus Christ, You are Peter, and upon this rock I will build my Church, cannot fail of its effect, the words spoken are confirmed by their consequences. For in the Apostolic See the Catholic religion has always been preserved unblemished, and sacred doctrine been held in honor. Since it is our earnest desire to be in no way separated from this faith and doctrine, we hope that we may deserve to remain in that one communion which the Apostolic See preaches, for in it is the whole and true strength of the christian religion.
I asked one of the SSPX apologists here about this and he told me that the Council was wrong, and said the same about Pope Sixtus IV's condemnation of "the Church of the City of Rome can err" as being "contrary to the holy Catholic faith" and as containing "manifest heresy" (Bull "Licet ea", Aug. 9, 1479). Go figure.
It is a Catholic dogma that the Apostolic See of Rome will always "hold out". Per the IVth Council of Constantinople:
We have to define what "holding out" is. That can't possibly mean papal impeccability. Right?
The first condition of salvation is to maintain the rule of the true faith.
Popes individually are not guaranteed salvation personally, correct? So, that would leave open the possibility of a Pope not maintaining the rule of faith in his person. Correct?
And since that saying of our lord Jesus Christ, You are Peter, and upon this rock I will build my Church, cannot fail of its effect, the words spoken are confirmed by their consequences. For in the Apostolic See the Catholic religion has always been preserved unblemished, and sacred doctrine been held in honor.
This then, begs the question: Just how bad can a Pope be? Where is the defined impossibility that the Apostolic See can't engage in? Once we find that untouchable place, everywhere before that point is possible.
I asked one of the SSPX apologists here about this and he told me that the Council was wrong, and said the same about Pope Sixtus IV's condemnation of "the Church of the City of Rome can err" as being "contrary to the holy Catholic faith" and as containing "manifest heresy" (Bull "Licet ea", Aug. 9, 1479). Go figure.
Was he a card-carrying member of the SSPX apologist's task force?
"I asked one of the SSPX apologists here about this and he told me that the Council was wrong"
Are you sure he didn't tell you that your interpretation of this passage is wrong?
I find nothing to disagree with in the passage, and nothing that contradicts SSPX.
Setting aside for the nonce matters of translation (which always makes me nervous), let's look at what it says.
"And since that saying of our lord Jesus Christ, "You are Peter, and upon this rock I will build my Church," cannot fail of its effect, the words spoken are confirmed by their consequences."
Okay. Our Lord built his Church upon that rock. All parties are agreed.
"For in the Apostolic See the Catholic religion has always been preserved unblemished"
. . . has always been . . . There's no promise for the future there. It doesn't say, "can never be attacked."
"Since it is our earnest desire to be in no way separated from this faith and doctrine, we hope that we may deserve to remain in that one communion which the Apostolic See preaches"
That's exactly what SSPX holds. However, they also hold that modenists within the Church are trying to separate the entire Church from its faith and doctrine (for which you can make a strong case), so they hold to the faith and doctrine, and the communion that the Apostolic See preached, at the time that document was written.
This entire line of argument, though, is begging the real questions.
Has the Church been under attack from within by those Saint Pius X called Modernists?
Have those Modernists introduced changes to the Catholic the faith and doctrine as it existed before they came along?
If so, what is their authority for so doing?