In the link to Popper's speech from my post 529, you'll notice that Popper had a lot to say about Marx including this (emphasis mine:)
The Marxist theory of history, in spite of the serious efforts of some of its founders and followers, ultimately adopted this soothsaying practice. In some of its earlier formulations (for example in Marx's analysis of the character of the "coming social revolution") their predictions were testable, and in fact falsified.[2] Yet instead of accepting the refutations the followers of Marx re-interpreted both the theory and the evidence in order to make them agree. In this way they rescued the theory from refutation; but they did so at the price of adopting a device which made it irrefutable. They thus gave a "conventionalist twist" to the theory; and by this stratagem they destroyed its much advertised claim to scientific status.
Also in reference to my previous post - in an attempt to illustrate why I see historical sciences as inferior to hard sciences, imagine how a jury would react to the summation arguments in a murder trial if the defense said "there is no evidence that my client committed this crime" and the prosecution responded with "just because there's no evidence doesn't mean he didn't do it (the absence of evidence is not evidence of absence)."
Indeed, the judge would have thrown the case out at the beginning rather than waste the court's time.
And therein lies the secret of the "magician's trick," the "Magic of the Extreme" first demonstrated in the intellectual life of Frederich Nietzsche, as subsequently adumbrated by the great German-American philosopher of history Eric Voegelin, my long-time teacher the "charm," the "Venus eye that fascinates," the "seductive force that emanates" so as to prevent us from seeing what the "left" and "right" hands [e.g., Good and Evil] are actually doing in the actual world....
Why this stratagem works so well nowadays is completely beyond my comprehension. It seems the only explanation is: Increasingly, the People have lost touch with Truth....
Thank you oh so very much, dearest sister in Christ, for your magnificent and deeply penetrating and luminous essay/post!