Oh, mulch and compost!
You know very well you would not vouch for every sentence in the 10,000 books written by the historic fathers of the Reformation, even though the major ones' works are still in print and taught in Bible colleges and Evangelical and Reformed seminaries and can be garnered off of websites from sea to shining sea.
"But we never said Philipp Melanchthon was infallible!" saith metmom in my imagination. To which I respond, "Nor Catherine either!"
This dictum that "if you haven't officially denounced this or that, you've accepted it" is nonsense: it's certainly not a rule you live by.
Every canon of Catholic law says that the devil is to be resisted; and that the authority of the pope is limited inasmuch as he cannot command error or evil, not propose an erroneous doctrine to be accepted d fide by the whole Church.
I think Catherine's statement about "even if the pope were Satan incarnate" is a dangerous bit of overheated rhetorical hyperbole, and if she were a FReeper I would be after her hammer and tongs.
("Oh, shut up, Catherine, you know that's not true. You've got the more-Catholic-than-the-Pope sedevacantists dangerously close to apoplexy, and you've got metmom's ears twitching and billowing smoke. And mine too! So cut it out!")
Enjoy this cheery 2-min video on infallibility and papal myocardial infarction. It's worth at least a little heh-heh.
I never made any claim that any church leader spoke infallibly.