There are the 9-11 Truthers...

…then there are the Fatima Truthers:

THE Vatican tried yesterday to draw a line under a conspiracy theory that has dogged the Catholic Church for decades - that it has been harbouring details of the predicted apocalypse.
The Pope's second-in-command, Secretary of State Cardinal Tarcisio Bertone, denied that the church was suppressing a vision of the end of the world said to have been revealed by the Virgin Mary to three shepherd children on a hillside at Fatima in Portugal exactly 90 years ago.

Hey, Fly! You guys holding out on us?

UPDATE from the 'fly - no. The anniversary of the apparitions was May 13, so it's a seasonal affliction. A lot of the 'secret of Fatima' seems like inside-baseball stuff and people read more into it than is really there. (These are usually the same people who reject actual doctrine as "too complicated.") So usually what you get is, "Ooooh! The Apocalypse! Lakes of burning pitch! This is the good stuff!" And then you tell them the truth, that the three parts of the secret have a) already been revealed, and b) already happened decades ago; and they say, "But that's BORING." Then they make one of two errors: they either go back to their lives as if the message was never important, or they say "Obviously there's some conspiracy or deeper truth we're missing - so what is it, really? Knights Templar? Da Vinci Code?"

In short, your description of them as "Fatima truthers" is perfect.

This may take a bit, so please be patient. (Then again, the official missive is a lot longer - Cardinal (then-bishop) Bertone starts off, and near the end there's a terrific commentary from then-Cardinal Ratzinger, plus reproductions and translations of Sister Lucia's original written letters.) In the middle of the link you find a great summation by Angelo Cardinal Soldano, given on May 13, 2000:

The vision of Fatima concerns above all the war waged by atheistic systems against the Church and Christians, and it describes the immense suffering endured by the witnesses of the faith in the last century of the second millennium.

Along the way, there's a lot of the sort of thing that makes Steven Camp's eyes go buggy - the 'three parts of the secret' talk a lot about Mary's role in the world.

Part 1 - the vision of Hell. Sister Lucia says that it lasted only an instant, but for all that, "I think we would have died of fear and terror" had they not been promised earlier by Mary that they would go to Heaven. (Alarm Bell #1 - who's Mary to say who goes to Heaven? The answer, of course, is that born-again believers say it of themselves and others all the time, without the advantage Mary has of already being there. They base this on Scripture, and the authority of the Holy Spirit. Well, so does Mary.)

Part 2 - the warning to devote the world (and Russia in particular) to the Immaculate Heart of Mary. Alarm Bell #2, big time. Ratzinger's commentary (awaaaaay down near the bottom of the link) explains why this isn't idolatrous - Mary's heart ("the centre of human life, the point where reason, will, temperament and sensitivity converge, where the person finds his unity and his interior orientation") was the greatest earthly example of unity with God's grace. "To be 'devoted' to the Immaculate Heart of Mary means therefore to embrace this attitude of heart, which makes the fiat - 'your will be done' - the defining centre of one's whole life. ...from whom might we better learn in every age than from the Mother of the Lord?" In short, we're not praying to her, but holding her up as an example all ought to strive for, unity with Christ. "Do whatever He tells you," as she herself said at Cana.

If one is disinclined to trust a guy who wound up being Pope, there's the evidence of history. In this part of the secret, Mary said that if Russia was converted, then there would be lasting peace; if not, "she will spread her errors throughout the world, causing wars and persecutions of the Church. The good will be martyred; the Holy Father will have much to suffer; various nations will be annihilated." Done, and done. Right after, she promises that Russia will be so consecrated and eventually converted, and "a period of peace will be granted to the world." This is really the only part that hasn't happened yet - Pius XII did the consecrating, and John Paul II extended it to the whole world, but it's been less than 20 years since the Soviet Bloc crumbled, so one must take a longer view.

Part 3 -

...pointing to the earth with his right hand, the Angel cried out in a loud voice: 'Penance, Penance, Penance!' And we saw in an immense light that is God: 'something similar to how people appear in a mirror when they pass in front of it' [and] a Bishop dressed in White. 'we had the impression that it was the Holy Father.'

Other Bishops, Priests, men and women Religious going up a steep mountain, at the top of which there was a big Cross of rough-hewn trunks as of a cork-tree with the bark; before reaching there the Holy Father passed through a big city half in ruins and half trembling with halting step, afflicted with pain and sorrow, he prayed for the souls of the corpses he met on his way; having reached the top of the mountain, on his knees at the foot of the big Cross he was killed by a group of soldiers who fired bullets and arrows at him, and in the same way there died one after another the other Bishops, Priests, men and women Religious, and various lay people of different ranks and positions.

Beneath the two arms of the Cross there were two Angels each with a crystal aspersorium in his hand, in which they gathered up the blood of the Martyrs and with it sprinkled the souls that were making their way to God.

This was written down in 1944 by Sister Lucia but not made public for many years; the attempted assassination of John Paul 2 is widely seen as an example of the described persecutions of the prophecy, but the great pogroms against faith conducted by the athiest powers of the 20th century are fulfillment enough, and many bishops and lay religious or many denominations shared in that. As Cardinal Ratzinger said in his commentary, is "will probably prove disappointing or surprising after all the speculation it has stirred. No great mystery is revealed; nor is the future unveiled." In brief, it's the standard warning of the Gospel - "Repent, for the Kingdom of God is at hand."

There is, though, Alarm Bell #3 - why the blood of the Martyrs, and not Christ? Ratzinger gives a good explanation, but again, not everyone trusts papal authority, so I'll use CS Lewis' "Mere Christianity." He describes the new life of Christ as 'a good infection': if you get close to Him, you will catch it and then spread it around. In Scriptural terms, we are made the Body of Christ. ("Why dost thou persecute Me? ... I am Jesus, whom thou art persecuting." -Acts 9:4, 5) That's what this sprinkling means - it means that the martyrs of the faith, His Body, by being united with Him, spread the new life to others. We are a community of believers united beyond time and place. The blood of men, powerless of itself, is in communion with Him and therefore brings Him to the world.

Now, people seize more readily on movie thrills: they don't really think about it, but instead settle for a vague imaginative picture - if you're lucky, you get something like "The Stand." More likely it's the Horsemen of the Apocalypse (looking rather like Brad Pitt, Russell Crowe, Hugh Jackman, and Christian Bale), doing the slow roll against a background of explosions while guitars wail. Then Walker, Papal Ranger (Mel Gibson), a former priest with a crisis of faith, roars into action. More stuff explodes, there's a hot sex scene, a heartfelt talk with an older mentor (Sam Elliott), big final battle with the Devil (Clint Eastwood), Jesus (Denzel Washington) literally saves, annnnnnnnd - credits!

Uhm... NO. Lewis writes elsewhere that 'quite ordinary people' are going to be doing the fighting, again echoing Scripture: God chooses the lowly and the humble to confound the proud and the mighty (1 Cor 1:25-29).

So, that's it. Turns out that it's just the Gospel, 'nothing exciting,' just the boring old great struggle of the Kingdom of God in revolt against the occupying powers of Hell for the fate of humanity, in which anyone may strike a crucial blow at the front lines, and become an eternal hero. Ho-hum.