Pius XII said so!
It is not to be thought that what is set down in Encyclical letters does not demand assent in itself, because in this the popes do not exercise the supreme power of their magisterium. For these matters are taught by the ordinary magisterium, regarding which the following is pertinent: “He who heareth you, heareth Me.” (Luke 10:16); and usually what is set forth and inculcated in Encyclical Letters, already pertains to Catholic doctrine. But if the Supreme Pontiffs in their acts, after due consideration, express an opinion on a hitherto controversial matter, it is clear to all that this matter, according to the mind and will of the same Pontiffs, cannot any longer be considered a question of free discussion among theologians.
— Humani Generis
Unless, of course, you are an LST, MST, SVST and Euntes theologian!
They'll tell you that an encyclical is not an ex cathedra statement so you need not follow it, like Humanae Vitae.
Even if the pope makes an ex cathedra statement like what Pius IX did in proclaiming the dogma of Papal Infallibility, they'll tell you that the Dogma is wrong.
Because these theologians in those DANG schools, well not all of them, only the nutty ones stuck in the hippie "Imagine all the People" '60s, think and believe only one thing.
THEY ARE THE ONLY ONES WHO ARE INFALLIBLE!
Makes sense right? It's just simple logic.
They don't want you to follow the Pope and the Church's Teaching Authority on faith and morals.
If you listened to them, who did you obey?