The Roman Catholic Church has hardly been unwaveringly inerrant.
Ergo, it is quite possible for one conscience to be correct while the official stance of Church & tradition be wrong - see the current Pope, of which one may validly ask “is the Pope Catholic?” in earnest and not merely in rhetoric.
A prime example of Luther’s conscience being correct while standing alone against the whole of Church & tradition is the then-popular notion of “indulgences”: that one could literally wash away sin by paying the Church a bribe - something which the Church officially held true, and supported by whatever twisting of tradition could be applied. (Don’t tell me it was somehow not “ex cathedra” or some such, we’re talking the Church officially sanctioning the alleged literal ability of someone to bypass the Crucifixion with cash.) This being no longer an official stance of the Church & tradition points to the non-inerrancy thereof in the face of a single voice standing for an unpopular (and unprofitable) truth.
HA!
So you get to define the terms of the “Teaching of the Church”?
Ex Cathedra means something.
The fact of Popes who failed in human conduct does not raise their failings to Doctrine.
Luther did NOT begin by fighting against the sale of indulgences, as that was an afterthought.
As noted in the article, Luther was promoting a new theology, which he at first insisted was in line with Catholic teaching.
In a 1516 letter he firmly acknowledged the primacy of the Pope and the authority of the Church and sought to debate certain matters with a Cardinal, asserting that he would concede to Church authority after having the debate.
Luther lost the debate, but rather than follow his promise he appealed to the Pope.
When the Pope refused his appeal he called for a ruling by some future Church Council.
Having failed in his final appeal, rather than stand by his earlier ascent to Church authority, he wrote on 11 Dec 1518, his belief that the anti-Christ was rules at the Papal Court.