R. Joseph B. Soloveitchik changed Jewish history with his 1975 address to the RIETS Rabbinic Alumni. In that speech, he denounced a plan to annul marriages, effectively campaigning against R. Emanuel Rackman’s candidacy for the Yeshiva University presidency and setting the boundaries of modern agunah advocacy.1 An earlier source sheds light on one of R. Soloveitchik’s main points, the religious purity of our Sages’ motives. Whoever doubts the Sages, taints them with accusations like misogyny, doubts Judaism.
R. Soloveitchik inferred this strong position from an unusual phrase in Rambam’s Mishneh Torah (Hilkhos Teshuvah 3:8). Rambam states that anyone who denies the Oral Torah or “contradicts its transmitters” (makhchish magideha) is classified as a heretic. What constitutes contradicting the transmitters of the tradition? R. Soloveitchik explained that it means questioning their motives, denying their spiritual uprightness, associating negative personal traits to the bearers of our tradition. Whoever rejects the great sages of every generations, even post-Talmudic, rejects the tradition they embody.
Historians and R. Soloveitchik enthusiasts may find it interesting that this was not a new interpretation innovated for this occasion, a convenient political weapon devised for the situation. R. Soloveitchik had published it 30 years earlier. In a 1943 lecture in memory of his father, R. Soloveitchik offered this explanation as part of a lengthy discussion of the laws of declaring the new month. He then published the lecture in the journal Ha-Pardes (17:10, Shevat 5704). You can find it online here: link.
Interestingly, that formulation proceeds from a more limited view. R. Soloveitchik distinguished between laws that the Sages received as tradition and those they derived through logic. Rejecting the Oral Torah refers to the tradition. Rejecting the Sages means disagreeing with their logic, their judgment as presented in the Talmud. From this limited requirement, R. Soloveitchik deduces that rejecting the Sages themselves constitutes heresy. He then applies it to the Sages in general, presumably even post-Talmudic bearers of the tradition. Someone who rejects their judgment, rejects the tradition.
This final step reflects R. Soloveitchik’s view 30 years later, when he articulated it in a communal controversy.
 See R. Steven Weil, “Mesorah: The Rav Speaks” in Jewish Action Summer 2011 for a summary of the speech: link