You are mixing apples and oranges. The Church never taught that slavery was permissible and certainly no Pope ever did.:
Popes having slaves is public enough to cause scandal and to teach the unwary that slavery is ok.
"For many centuries the Church was part of a slave-holding society. The popes themselves held slaves, including at times hundreds of Muslim captives to man their galleys. Throughout Christian antiquity and the Middle Ages, theologians generally followed St. Augustine in holding that although slavery was not written into the natural moral law it was not absolutely forbidden by that law. St. Thomas Aquinas, Luther, and Calvin were all Augustinian on this point. Although the subjection of one person to another (servitus) was not part of the primary intention of the natural law, St. Thomas taught, it was appropriate and socially useful in a world impaired by original sin. " - Cardinal Dulles
firstthings.com/article/2007/01/development-or-reversal-37
Slavery is a matter of faith and morals, thus the position of the doctors of the church who thought it permissible under some circumstances is scandalous. Equally, current Catholic teaching refers to it as an infamy, but not an intrinsic evil.
The abuse of indulgences was never approved by the Church and certainly not by the Pope.
The indulgences that are most bothersome are those personally signed and authorized by the Pope which granted plenary indulgence AND remission of all sins in exchange for donations to the building of St Peters. This became the cause of great scandal at the time and led to attacks from many corners including Wittenberg university’s Martin Luther. Luther’s attacks would later be brought to trial, at which time he began to rethink and reject a whole host of church teachings. Ironically, after Luther was thrown out of the Church, the Church did reverse itself on the indulgence, however by that time Luther had already embraced a host of other reform stances, so the reversal came too late to stop the Reformation snowball. Protestant Source: Here I Stand pg 55-200
The Catholic encyclopedia confirms that the indulgences were authorized by the Pope, bold added:
"The epoch-making event connected with the publication of the papal Bull of Indulgences in Germany, which was that of Julius II renewed in adaptable form by Leo X, to raise funds for the construction of St. Peter’s Church in Rome, brought his spiritual difficulties to a crisis.
Albert of Brandenburg was heavily involved in debt, not, as Protestant and Catholic historians relate, on account of his pallium, but to pay a bribe to an unknown agent in Rome, to buy off a rival, in order that the archbishop might enjoy a plurality of ecclesiastical offices.
For this payment, which smacked of simony, the pope would allow an indemnity, which in this case took the form of an indulgence. By this ignoble business arrangement with Rome, a financial transaction unworthy of both pope and archbishop, the revenue should be partitioned in equal halves to each, besides a bonus of 10,000 gold ducats, which should fall to the share of Rome.
…It is not denied that a doctrine like that of the indulgences, which in some aspects was still a disputable subject in the schools, was
open to misunderstanding by the laity; that the preachers in the heat of rhetorical enthusiasm fell into exaggerated statements, or that the financial considerations attached, though not of an obligatory character, led to abuse and scandal. The opposition to indulgences, not to the doctrine—which remains the same to this day—but to the mercantile methods pursued in preaching them, was not new or silent. Duke George of Saxony prohibited them in his territory, and Cardinal Ximenes, as early as 1513, forbade them in Spain. "
newadvent.org/cathen/09438b.htm
So I am left with doctrine, which is to be accepted as infallible, but which may be allowed to be misunderstood, abused, and scandalized even within infallibility? This really undercuts my whole understanding of what infallibility means. So if I follow Cardinal Dulles correctly, then only the original doctrines are infallible, NOT the current application in any specific culture. This seems to coincide with the liberal interpretation in practice or moral application, though not in theory. For example, it would be licit for the Church to change the application of the commandment that thou shalt not commit adultery in relation to birth control and so on as liberals have pressed for, so long as the Church continues to affirm the doctrine of no adultery. Thus it would appear that the laity have misunderstood the position of the church in regards to infallibility to mean that the teachings are infallible, when instead the Church only means that the original or most basic teachings are and not the applications.
