Hi Sid. Thank you for joining in on the discussion. I will answer your remark, but I really think we are starting to digress into the topic of infallibility, which would be best discussed in another thread. I will answer both to set the record straight concerning your query and because of infallibility’s link to the inerrancy of Scripture, since the Church has constantly and universally taught that the Bible is without error for over 2000 years.
First, regarding slavery, the Church never officially condoned slavery stating that it was a just practice or that it was a dogma of faith or morals that masters have a right to own slaves. In fact, the Church, morally speaking, was the one to condemn the practice of the exploitation of slaves and the manifestation of slavery in the New World.
Second, regarding the eastern Churches, a quick Google search on the topic will help clear up your confusion on their position on this issue. Here’s a site that explains that the eastern Churches have always held that artificial contraception is morally evil, despite the fact that in recent years some
local churches have taught contrary to the constant teachings of the Church.
roca.org/OA/155-156/155h.htm. If individual bishops embrace heresy, that does not change the constant and infallible truths that they oppose. In order for a teaching to fall under the universal and ordinary Magisterium, it is the bishops
in union with the pope who determine infallible truth, not by necessarily even unanimous teachings but by the constant teaching of the Church when the bishops make a definitive judgment on a matter of faith or morals.
The Church’s teachings are not based on novelty or innovation; they are grounded in apostolic Tradition. Therefore, if the Church has always condemned something to be sinful, then it is an infallible truth of morals that cannot be changed. You can try to argue it all you want, but we have at least two papal declarations condemning the practice of artificial contraception as not only a morally unjust practice but as
intrinsically evil. Artificial contraception is not a new practice, and the Church has always condemned it as evil.
catholic.com/library/Birth_Control.asp