In the complete version, Benedict's rejection of the "foolish prejudice" against Francis stands on its own. It's something good Catholics should work hard to avoid, and the main emphasis of the letter. Solo a margine — "only on the side," he notes his surprise that Professor Hünermann was featured among the authors of the small theological works in question. He describes him as having "virulently attacked the magisterial authority of the pope, especially on questions of moral theology."
If anyone benefits from this call to arms, it is Pope Francis. It's his teaching authority and responsibility, after all, that Benedict wishes to defend, both by correcting the "prejudiced" viewpoint and by a specific, academic critique.
The Secretariat for Communications, on the other hand, who originally published the letter and hand-picked portions of it to use for marketing, wished to be seen as avoiding "foolish prejudice." But the move demonstrated a lack of serious concern for "interior continuity" — including mounting a robust defense of the Petrine office.
In 1984, then-Cardinal Ratzinger spoke of the relationship between bishops and moral theologians this way:
[The moral theologian] helps toward the understanding of the moral demands of the Gospel in the particular conditions of his day and so serves the formation of conscience. In this way he serves also the development, purification, and deepening of the moral message of the Church. [...] The teaching office depends on the specialized knowledge of the experts and must let itself be thoroughly informed by them about the content of the matter in question before making an utterance regarding new problems. (On Conscience, Ignatius Press, 71-2)
Stifling Pope Benedict's voice, who in his current capacity is perhaps the moral theologian par excellence, endangers not only the clarity of the moral message of the Church, but perhaps, even to some small extent, the formation of Pope Francis's own conscience. Not because Benedict exercises a parallel magisterium over and against Francis, but because Benedict is a bishop and theologian with a mind and heart that demand the utmost attention by all Christians, Francis included.
It is almost impossible to know what, if any more, correspondence regarding the volumes has occurred between Benedict, Francis, and members of the Vatican news services and publishing house. It would be rash to assume that Pope Francis is not aware of his predecessor's academic reservations about Hünermann. Perhaps he is even swayed by them. Certainly, Francis is personally familiar with the thought of Professor Hünermann. The two have known each other for decades, and had a meeting which touched on the subject of Amoris Laetitia. Francis might even be swayed by some of Hünermann’s ideas. Nevertheless, the pope has a vast prerogative to speak and write as he sees fit within the bounds of the magisterium. Even more so, to seek in charity whatever truth may be acquired from the writings of others, even if those writings, or the ideas that shape them, are imperfect and in some ways problematic.
However, there is no prerogative for contravening the reasonable formation of conscience for any person. Nor for suggesting at all that the papal teaching office is being decoupled from the Church's active moral and theological tradition.