Fr. Longenecker describing the type of complete loss of faith where the person thinks they are more faithful than everyone else. See “The most common way to lose the faith….” I say this is the main problem with the papal critics — by which I mean the papal accusers (not those with limited faithful critiques).
They believe themselves to be more faithful than the Pope, than the Magisterium, than the Church herself. They say they have faith, but they only believe what their own mind tells them is true. And that is no different from atheism. Literally no different. The atheist agrees with the Church, whenever the Church’s teaching happens to coincide with his own ideas. So does the papal accuser.
It is dogma that the Church is indefectible, that the Pope has the gift of truth and a never-failing faith, and it is a theologically certain conclusion, then, that the body of Bishops can never follow a false head (antipope or invalid pope), that the Pope can never teach or commit heresy (nor change from being valid to invalid), and that the Pope can never lead us astray.
Those who accuse the Pope of heresy, apostasy, or idolatry, along with those who put themselves above any Pope, any Council, or the body of Bishops to judge when these are correct and incorrect, have no faith at all. They cannot claim to have the faith of a Protestant, since they reject Protestantism and call themselves Catholic. They cannot claim to have the implicit faith of some atheists, as they have no faith in love, mercy, justice, and truth. Having faith only in themselves and in a certain subculture, they are idolators, heretics, and apostates. They are what they fear will harm the Church. They are what they accuse the Pope of being. They condemn all who disagree with them. With their own judgment will they be judged.
RLCJ
the reproach of Christ 
I am in the process of studying to join Fr.Hardons Marian Catechist Apostolate. In lesson 5 it talks about how the Pope can be a heretic as long as he is not speaking as the Magesterium. Atleast that’s how I understood it.
https://mariancatechist.com/course-number-one/
The First Vatican Council infallibly taught that each Pope has the gift of truth and a never-failing faith. This dogma necessarily implies that a valid Pope can never teach or be a heretic in any way, just as Ss. Robert Bellarmine and Alphonsus Liguori taught. Also, since the Church is indefectible, a Pope accepted by the body of Bishops as the Roman Pontiff cannot possibly be invalid.
Consider the case of Pope Vigilius. While Pope Silverius reigned, Vigilius was an antipope and a heretic. When Silverius died and Vigilius was installed as Pope, he immediately abandoned his heresy and defended the true faith. The prevenient grace of God, which no one can resist, causes all valid Popes to be free from heresy, apostasy, and idolatry.
https://ronconte.com/2020/01/04/what-if-a-heretic-were-elected-pope-2/
We hear at about 16:30 on the link above how the Pope can sin and lead people into heresy.
It is a continuing problem in the Church that some of the faithful put certain teachers or sources above the Magisterium.
Thank you, I appreciate the response and the correction. I may email the Apostolate and explain the Pope cannot teach heresy or be a heretic in any way.