For much of the 20th century, in large parts of the world, the Stalinist movement on the one hand, and the Catholic Church and its political and social movements on the other, were the great antagonists.
Yet the Stalinist movements and the Catholic Church were, as was often pointed out, in many respects similar, parallel in their mindset and organisation.
It now turns out that they were similar in their attitude to mass rape by their "soldiers" in the field.
In 1945, when the gruesomely misnamed "Red" Army advanced into enemy countries in Eastern and Central Europe, the soldiers of Stalin's army raped vast numbers of women. In Berlin and Vienna alone, many tens, perhaps hundreds, of thousands of women were raped. Being raped was a common experience for that generation of German women.
Where American soldiers in Europe were hanged for rape, the attitude of the Russian government and of the army leaders in the field was to give their soldiers tacit licence for it. They regarded it as a right of the conquerors.
The ultra-chauvinist and even racist anti-German propaganda in which the soldiers had been educated prepared them to do what they did and to take an indulgent and collusive attitude to what others did.
Has the attitude of the Catholic hierarchy, up to the Pope, to the mass raping of children, over decades, by Catholic priests, and to the child-raping priests, been any different?
Everywhere the Church hierarchy covered it up, protected paedophile priests, actively worked to stop them being exposed. When scandal began to grow around the head of a paedophile priest in his parish, the hierarchy moved him somewhere he wasn't yet known. That is, they moved him to where he had a fresh crop of child victims to prey on!
That is the most astonishing thing - that the hierarchy did not see child rape as something they would work to stop. They routinely moved known paedophile priests to fresh territory.
In a Church notorious for its savagely repressive attitude to sexuality, all sexuality, very large parts of the hierarchy tolerated, and by their silence colluded in, the practice of a sexuality that is vicious and indefensible, not according to the laws of some imaginary God but according to the most basic values and instincts of everyday decent humanity.
Hypocrisy, certainly, but surely more than that.
Psychologically the great mystery is how those who regarded themselves as moral people could do what they did, and do it over years and decades.
Pointing to the parallel between the Pope's priestly army and Stalin's raping "Red" Army is not unfair to the priests. If anything it is unfair to the "Red" Army.
They were soldiers who had come hot from fighting tremendous battles, who had experienced and seen the devastation of the Ukraine and Russia by Hitler's armies. They had been brainwashed to regard Germans as evil in their "warlike" nature.
The priests? Both the rapists and the Church-hierarchy colluders operated over many decades - centuries, most likely. They had abundant time to think about it.
Maybe the psychological explanation is that if all sexuality is dirty and sinful, then the moral sensibility weakens and becomes half-blind. The special horror of this indefensible sexuality becomes indistinguishable from victimless adult consensual sexuality. The Church's hostility to sex produces a form of moral and social colour-blindness.
Pope Benedict cannot have been unaware, as he worked his way up the Church hierarchy, that many priests routinely raped children. It has been alleged that he himself was involved in one cover-up operation.
In any case he is the Fagin of the priestly army that still has many child rapists in its ranks. It is one of the crimes - and not the least one - of the Blair-Brown government that they invited him to visit Britain.