The recent history is that Humanae Vitae was promulgated to preserve the myth of unchanging moral truth. Indeed, yesterday's article by MSW was full of assumptions that AL was invalid because it did disagree with Veritatis on the same topic. It is a childish worldview and spawned the aphorism that consistency is the hobgoblin of small minds. The Trads in the Curia are constantly fearing that if they admit to error on a moral teaching, like birth control or homosexuality, that their whole intellectual house of cards will fall.  Of course, the reverse is true. People who have faith and courage enough to admit error actually inspire the trust of the faithful. If their worldview is based on never making a mistake then they will never accept that homosexuals are born not self-chosen. The tragic thing is, people actually suffer real consequences of their arrogance. Drag queens will enter Heaven before they do, if only because the Queens are more fabulous.