@ Marlelar: You are most welcome.
@Nishant2011: Although I'm only an unworthy defender of the reputation of the saintly Archbishop Thuc, I feel compelled to do what little I can to uphold his sacred honor. I fear that your somewhat too clever effort to besmirch his memory reveals the errors so typical of oversimplifications. Why can't it be entirely possible both for John XXIII to have at one time been a legitimate Pope and then later on to have ceased to be one? As you probably know, John XXIII is the most complicated and difficult Bishop of Rome to categorise in the first place, so extra care should be taken when the good Archbishop Thuc referred to him.
The most accurate explanation I can come up with to explain John XXIII does justify Archbishop Thuc's references to him. It is simply that perhaps John XXIII was that peculiar thing we call a "private heretic." He had heretical sympathies with the dangerous Italian early modernist Deist and Radical Liberal Antonio Rosmini that were strictly private and therefore quite consistently never revealed in public. Therefore it is entirely possible and Catholic to suppose that the Pontificate of John XXIII may have been legitimate if such were the case. Needless to say, this would then already be a case much more difficult for us to deal with than anything involving even the most controversial previous Popes like Liberius or Alexander VI.
If my theory should be correct, then John XXIII could easily have gone into a PUBLIC heresy perhaps beginning with his opening speech to the alleged "Second" Vatical Council in October 1962 (presuming there actually ever were such a legitimate Ecumenical Council, of course). That presumably heretical speech is said to have been written by that Communist abomination and Soviet agent Montini who later went by the name of "Paul VI" and my sense is that at that time John XXIII passed over into PUBLIC heresy and thereby ceased to be the legal and legitimate Pope of the Roman Catholic Church.
This view is entirely possible and consistent with Catholic theology so it's inconvenience and high degree of complexity does not by any means rule it out as something that could occur by God's forbearance. That would also leave us with precisely the complex situation that the good Archbishop referred to in his famous Letter of 1982: with the legality of John XXIII's acts from before October 1962 and the illegality of his acts after that date. But if this isn't complicated enough for us, it may also be that perhaps the Pontificate of John XXIII actually passed over into true public heresy only perhaps in March 1963 when the wicked Montini (the soon-to-be usurper Anti-Pope Paul VI) actually violently took over the Vatican from its legal occupants with massive assistance from the Soviet K.G.B. of that time.
At any rate, at some point from about October 1962 to March 1963 the Bolsheviks took over the Vatican and the Papacy was usurped. If so, then the non-mutilated Missal of 1962 would be legal and valid, yet the last acts of John XXIII would not be. And we would be in the difficult position of having to tolerate considerable confusion among sincere Catholics about the Pontificate (or non-Pontificate) of John XXIII because that specific time in our Church history is indeed singularly confusing!
Be this as it may, my explanation then would fully justify the later position of the saintly martyr to the faith Archbishop Thuc of Hue, Viet Nam. Whether we happen to fully agree with this view of Church history or prefer some other view of those uniquely confusing times, we should charitably give the late Archbishop Thuc some slack and not cast all-too-easy aspersions against him from, so to speak, the "peanut gallery" of our own later historical hindsight. Whatever the exact historical truth may be about John XXIII, we ought to go easy on Archbishop's Thuc's awesomely brave and courageous efforts to save the most holy apostolic succession of our beloved Holy Mother Church!!
(The other side of this is that we should be saving our brickbats to throw against the villainous Paul VI, not against the saintly Archbishop Thuc.)
So I've now done my small part to defend the sacred memory of the late Archbishop and his legacy. Therefore I must now respectfully desist and say no more on this thread...