There is something off kilter about His Excellency's initial disclaimer about modesty and not wanting to accuse anyone or criticize his superiors given the horrendous nature of what he proceeds to denounce. Why BE so modest? Why NOT accuse? Why NOT criticize? After all, he is not discussing things like seminarians ditching the soutane when they go out in public. He is analyzing the mark of the Beast.
"I speak to THEE, O mitered one!" St Anthony fulminated against a wayward bishop who was not even guilty of any infraction against the Faith or the faithful. Which for all we know had in Italian or Latin the sound of, "Hey, you there in the miter! That's right, I'm talking to YOU!"
How many superiors does a bishop have anyway, strictly speaking? I could be wrong, but I think that unless he is some kind of adjunct he has no direct superiors but the Pope, all others, such as cardinals in Rome or occupants of especially honored sees, falling in the category of lateral superiority.
I think that the disclaimer is the key element in the letter. And that it goes to show why there was no proper reaction against Vatican II on the part of cardinals and bishops who knew that it was a snare for the faithful.