As often happens, bad will and resistance to the truth leads to stupidity. St. Thomas taught that the intellect naturally tends to truth ... except when obstructed by bad will.
You are both at once ignorant of Church history and struggle with reading comprehension, and this is compounded by what can rightly be called a popolatry.
Honorius was anathematized by the Third Council of Constantinople, an anathema that was confirmed and ratified by Pope Leo II, who then added the explanation that it wasn't for pertinacious adherence to heresy himself but for neglect, a failure to condemn, allowing heresy to flourish and thus to be used as a tool of Satan for the spread of heresy. Honorius' failure was trivial compared to the failures of Pius XII, his failure to condemn Modernism, giving it countenance in many areas, and appointing one Modernist heretic after another to episcopal Sees. Honorius was anathematized 40 years after his death. Whether or not the same fate befalls Pius XII, if you were possessed of any reading comprehension, you'd see that I said that if Pius XII isn't anathematized then it owes an apology for Honoroius, which expression means that the Church saw fit to anathematize Honorius for MUCH less that Pius XII did. It's similar to the expression that "if God doesn't destroy the United States [or Tel Aviv], then He owes an aplogy to Sodom and Gomorrha". It's a rhetorical expression that evidently you are too dense and blinded by your exaggeration of papal infallability and impeccability to properly comprehend.
In any case, take a look again at the Cadaver synod as well, where Formosus was disinterred, condemned, thrown into the Tiber, the proceedings having been presided over and approved by another Pope, Stephen VI. But then Formosus' body somehow floated shore, and so a popular uprising removed and imprisoned that Pope. Then two subsequent Popes annulled the cadavers synod, reinterred Formosus, annd condemned Stephen VI. But then ANOTHER Pope came along, one who had voted to condemn Formosus at the original synod, and reaffirmed the condemnation of Formosus, having inscribed words of praise on the tomb of Stephen VI.
So, it's the example of Honorius that Cardinal Franzelin uses as a caution to avoid exaggerating the scope of papal infallibility.
Unfortunately, in reacting against R&R, who have effectively gutted the Church's indefectibility by reducing the protection of the Holy Ghost over the Church and the Papay to the one-or-twice-per-century solemn dogmatic definition, the SVs have exaggerated the scope of papal infallibility to the point of absurdity, and to an extent that NO THEOLOGIAN between Vatican I and Vatican II ever taught. Many popes made errors, even in the docuмents they promulugated as Pope (vs. private theologian). There was much debate about whether Honorius' letter to Sergius was meant as an ex cathedra pronouncement. Another famous case had Innocent II proclaming, in a Magisterial docuмent, that the Mass was valid even if a priest merely thought the words of consecration. St. Thomas took him to task for that error.
Finally, the SVs engage in confirmation-bias-driven appeal to authority, where they puff up the authority of docuмents they like (that promote things they agree with) but then simply ignore the ones they don't like. So, for instance, a teaching of the Holy Office clearly taught that explicit belief in the Holy Trinity and Incarnation are necessary by a necessity of means for salvation, but that doesn't stop most SVs (ignoring that ruling) from continuing to claim that infidels who believed merely in the "Rewarder God" can be saved.
Apart from the CMRI, the rest of SVs reject the Holy Week Rites promulgated by Pope Pius XII because they were defective, tainted with Modernism, etc. ... despite from the other side of their mouths preaching that Popes are infallible in doctrine and discipline pretty much every time they pass wind.
This self-serving confirmation-bias-based filtering leads to self-contradiction and inconsistency, aka hypocrisy.
Let St. Robert Bellarmine correct you, once again, on your mistaken assessment of the Pope Stephen VI and Pope Formosus case:
“The Twenty-Seventh Pope is Stephen VI, who can be joined with the Twenty Eight Pope accused of error, Sergius III. It is certain from Platina and others, that Stephen invalidated the acts of Pope Formosus, his predecessor, and commanded those ordained by him to be ordained again. Hence he thought that the Sacrament depended upon the virtue of the minister, which is a manifest error in faith. For that reason, Pope John IX afterward invalidated the acts of Stephen VI and approved the acts of Formosus. But a little afterward, Sergius III again invalidated the acts of Formosus, and hence also of John, and approved the acts of Stephen. Necessarily, one of these Popes was opposed to the others and erred, as the Centuriators diligently observed.
I respond: Stephen VI and Sergius III erred in a question of fact, not of law, and gave a bad example, not false doctrine. This is the history. Formosus, the Cardinal Bishop of Portus, was deposed by Pope John VIII, and demoted and returned to the lay state, after which he swore that he would never return to the city, or the Episcopate. A little after the death of John VIII, his successor, Martin II absolved Formosus of his careless oath, and restored him to his original dignity. Not long after that, Formosus was created Pope. He lived for five years and died. Stephen VI succeeded him who, being enkindled with great hatred against Formosus (or else unaware or not believing that he was absolved of his oath by Pope Martin), decreed publicly in a Council of Bishops that Formosus was never a legitimate Pope and therefore, all his acts were invalid. He compelled all those who had received orders from him to be ordained again, just as if they had received nothing. This deed displeased everyone, and therefore three Popes in succession, Roman I, Theodore II and especially John IX, after calling another Episcopal Council, judged that Formosus was a true Pope and invalidated the sentence of Stephen VI. Next, Sergius III succeeded him and imitated Stephen VI in all things. The particular question was whether Formosus was a legitimate Pope. We do not deny that in such questions Popes can err, and Stephan and Sergius erred in fact. But you will object: Stephen and Sergius not only judged that Formosus was not a true Pope, but even the sacred orders which he conferred were not valid; such is a manifest error against faith. For, even if Formosus was not a Pope, and always remained deposed and demoted, still, because he was at one time a true Bishop, and insofar as the character and power of orders cannot by any means be taken away, it is an error in faith to say that the sacred orders he conferred were not true orders. I respond: Stephen and Sergius did not publish some decree whereby they determined the orders by a demoted Bishop, or the orders that Formosus by name conferred after he had been demoted, must be conferred again, rather, they only de facto commanded them to be conferred again. Such a command proceeded not from ignorance or heresy; but from hatred against Formosus. Sigebert remarks in his Chronicle for the year 803 that Stephen VI was forcefully opposed by all those who were ordained by Formosus.“