Being a “member of the Magisterium” does not mean that one is infallible, and ALL who voted contrary to Pope Paul’s definitive teaching against contraception in Humanae Vitae, which has the infallible doctrine, were proved to be in error. Any of them not accepting that are in dissent.
Pope Pius XI in *Casti Connubii *(1930) had already declared infallibly that contraception was gravely evil, and the Commission to deliberate on the “Pill” had no mandate to deliberate on anything else. Those not accepting the infallible declaration in Humanae Vitae were again wrong.
Papal infallibility is a relatively new concept, finding its way into acceptance in 1870, as part of the first Vatican Council. It was hotly contested during discussions at the council and did not sit well with many Catholic religious and lay persons. The council outlined conditions which must be met for something to be considered infallible. And strangely enough, it made it retroactive.
Many theologians from the time of the proclamation thru today have had problems with the concept. They can point to numerous examples where papal infallibility as applied by 1st Vatican Council standards has proven to be quite fallible. My favorite was Pope Liberius, who had Catholics ditch the Nicene Creed so he could keep his job.
There is a modern theologian, probably familiar to many in this forum, Father Kung. He challenged others in the faith to discuss the concept. One of the people who took up the challenge was Father Ratzinger (later to become Pope Benedict). Father Ratzinger expressed his own concern over the concept. He wrote in “The Problem with Infalliability” (1974), “A predominantly critical article should not, however, ignore the positive side of Kung’s book. This can be clearly deduced from all that we have said before, when we affirmed that he opened for discussion, in an explicit and unequivocal way, problems that must be reformulated. He denounced obscurities in the historic and systematic structure of Catholic theology, which in fact have persisted and until now have usually been avoided and not confronted head-on” …… "I want to emphasize again that I decidedly agree with Kung when he makes a clear distinction between Roman theology (taught in the schools of Rome) and the Catholic Faith. To free itself from the constraining fetters of Roman Scholastic Theology represents a duty upon which, in my humble opinion, the possibility of the survival of Catholicism seems to depend.”
I think that some popes feel the power of their office and enjoy wielding it. Pope Pius would be a good example of this. Then you have the more humble servants of God like Pope John XXIII who once remarked: “I am only infallible if I speak infallibly but I shall never do that, so I am not infallible.”
If we could prove papal infallibility, many arguments here would be made moot. But the fact that there exist so many examples of the fallibility of papal infallibility, we need to be more discerning when it comes to walking the path of Christ.