Why is it that Catholics here are so very forgiving of the wicked popes in the history of their church yet rant and rave over Martin Luther - who was not guilty of anywhere near the same kinds of depravity that these so-called anointed of God successors of St. Peter were? Luther is not the Pope of Protestants.
I find it impossible to believe that those very top leaders of the Roman Catholic Church - those who were elected to that position by other so-called men of God - would have made it one day in the era of the Apostles had they done half the things these chaps did. If Catholics wonder why non-Catholic Christians reject the authority of the Pope of Rome over all of Christendom, they need only look to their own history of corruption which was so blatant, no one even tries to rationalize it away anymore. Add to that the corruption of the Gospel and it should be plenty plain to understand.
Yes, God will preserve His church, but that church is the Body of Christ and is made up of genuine Christians who, like living stones, are being built up as His spiritual house (I Peter 2:5). No earthly institution has a corner on that designation and that is why we know that the Body of Christ, of which we are members who belong to Him, will be presented spotless and blameless at His coming. It is Him who is able to keep us from stumbling, and to make us stand in the presence of His glory blameless and with great joy (Jude 1:24).
That he might present it to himself a glorious church, not having spot, or wrinkle, or any such thing; but that it should be holy and without blemish. (Ephesians 5:27)
Again, a straw man. Nobody is excusing improper behavior on the part of any Pope.
Let us consider the US. There have been several duly elected Presidents who have acted terribly while in office (both official and personal behavior), bringing negative consequences to the nation.
Was the Constitution at fault? Did we all just give up on the Constitution? Did the entire union dissolve? Nope.
There was a Civil War. What was the result?
Now consider the Roman Catholic Church. Have there been some Popes who worked against the Church? Yep. Were the teachings of the Church wrong? Nope. Has there been upheaval? Yep. Have their been changes to improve the situation? Yep.
So there you have it. In both cases, the institution wasn’t at fault. Individuals were. The institution took self-correcting action. As humans, we are imperfect and will continue to be so.
Regarding Luther, his actions stand on their own.