I agree with everything you have said. But I do not see the Bishop’s reservations on private revelations to be uncharitable. Perhaps my point is this is nothing compared to, for example, a Bishop failing to defend Humanae Vitae.
Regarding private revelations (such as Fatima), we read - from EWTN - “Some private revelations, however, the Church has accepted as credible, calling them constat de supernaturalitate (that is, they give evidence of a supernatural intervention). Such private revelations cannot correct or add anything essentially new to Public Revelation; however, they may contribute to a deeper understanding of the faith, provide new lines of theological investigation (such as suggested by the revelations to St. Margaret Mary on the Sacred Heart), or recall mankind prophetically to the living of the Gospel (as at Fátima). No private revelation can ever be necessary for salvation, though its content may obviously coincide with what is necessary for salvation as known from Scripture and Tradition. The person who believes the teachings of the Magisterium, utilizes devoutly the sacramental means of sanctification and prayer, and remains in Communion with the Pope and the bishops in union with him, is already employing the necessary means of salvation. A private revelation may recall wayward individuals to the faith, stir the devotion of the already pious, encourage prayer and penance on behalf of others, but it cannot substitute for the Catholic faith, the sacraments and hierarchical communion with the Pope and bishops.
Another way of saying this is that private revelations may not be believed with divine and Catholic Faith. They rest on the credibility of the evidence in favor of a supernatural origin. In the case of private revelations approved by the highest authority in the Church we can say with Pope Benedict XIV,
Although an assent of Catholic faith may not be given to revelations thus approved, still, AN ASSENT OF HUMAN FAITH, made according to the rules of prudence, IS DUE THEM; for according to these rules such revelations are probable and worthy of pious credence. [De Serv. Dei Beatif.]
The Pope is saying that a Catholic, seeing that the Church (and here the Holy See is meant, as only it’s acts can be of universal effect) has investigated and approved certain revelations, is being prudent to give them human assent. That acceptance does not rest on the guarantee of Faith, or the charism of infallibility, but on the credibility of the evidence as it appeals to reason. The assent involved is not supernatural but the natural assent that the intellect gives to facts which it judges to be true. Approved private revelations are thus worthy of our acceptance and can be of great benefit to the faithful, for as the Catechism of the Catholic Church notes, ‘Guided by the Magisterium of the Church, the sensus fidelium knows how to discern and welcome in these revelations whatever constitutes an authentic call of Christ or his saints to the Church.’ [CCC 67]
However, on the other hand, they do not demand acceptance by Catholics. As Pope Benedict states in the aforementioned text,
it is possible to refuse to accept such revelations and to turn from them, as long as one does so with proper modesty, for good reasons, and without the intention of setting himself up as a superior. [De Serv. Dei Beatif.]”
Notice the wording here. If one chooses to refuse to believe in a private revelation such as Fatima, one must do so with 1. Proper modesty, which means one doesn’t publically challenge the private revelation or ridicule it before others; 2. For good reasons (not completely arbitrary ones; and 3. without the intention of setting oneself up as a superior: e.g., “I know better than the Holy See.”