One of the fruits Catholics sometimes pray for in this mystery is "purity of mind." Of course, Americans, being apostate Puritans, tend immediately to think this means, "Don't let me smile at a risque joke, Lord." But that's not really what is meant by mental purity.
The Church teaches that part of the effect of the fall is the "darkened intellect." This doesn't mean sin necessarily makes you unintelligent. Great sinners have been highly intelligent and cunning. But it does mean that sin makes you stupid about eternal things. The great illustration of this is the devil himself. With great cunning, the fallen angel, possessing intellectual powers far surpassing anything human, engineers the murder of the Son of God, only to be overwhelmingly defeated by his own schemes like a cosmic Wile E. Coyote. Even in our own race, we see the darkened intellect of a man like Hitler, using cunning and guile to gain power and running rings around his enemies as he gains victory after victory in the conquest of Europe. But his darkened intellect blinds him to his own stupidity, and so his idiotic racism and pride commits him to letting the British army escape at Dunkirk, throwing an entire army away at Stalingrad, diverting the dwindling resources of his Reich to an insane campaign of mass murder even as that Reich is collapsing around him, and to blaming and shooting everybody else for the results of his own loony orders. Sin has the strange effect of making people clever about things that destroy while rendering them imbeciles about the things of God.
On a human level, the sins of the intellect are on full display in the sheer gratuitous cruelty of the Crowning with Thorns. It's a picture of the human race at its most exquisitely vile — and at its most noble. The soldiers responsible for flogging Jesus are, up till this point, just doing their jobs. Brutal, to be sure. But they needn't have anything personal against the prisoner. He's just another damned dirty criminal sent down by headquarters If they retained a shred of their humanity they might have just processed him and sent him on his way to execution like good little thugs.
But no. Sin's corruption is to be on full display in this execution. The soldiers inflict on Jesus a brutal scourging but even that's not enough. They now feel the need to play and get in touch with their creative and childlike impulses. So they parade Jesus before the whole Cohort and hail him as "Imperator." They put a reed in his hand, mimicking the lictors' rods for the consul (from which the Field Marshal's modern baton is descended), representing the power to chastise and to lead. They clothe him with a legionary uniform.
Finally, out of a chemically-pure cruelty they take their God-given capacity for play, for creativity, for problem-solving, for art, and for humor — and twist them all into a crown of thorns to press down on the head of a man Who has already been beaten nearly to death. The sheer gratuity of the act takes my breath away. It's almost the perfect parody of love in its complete freedom. Nothing about this act of refined savagery leaves any room for whining about environment, or a bad childhood, or any of the other Usual Suspects in the Blame-Shifting Game. Here is Man, acting with complete freedom and choosing to use that freedom for completely demonic ends.
But even more breathtaking is the Son of Man, silent as a sheep before his shearers, an unbearably noble figure who not only endures such cruel humiliation, but who endures it for these creatures, thereby showing forth a glory to which his tormentors are blinded by their darkened intellects. For the Roman legion had an award, called the "corona graminea" ("grass crown") which was woven from the grass on the field of battle and given to a man who, by single-handed action, saved the entire legion from destruction.