He describes someone reading a story about the enemy and then finding out that the enemy didn’t do it or wasn’t as bad as the story said. “Is one's first feeling, 'Thank God, even they aren't quite so bad as that,' or is it a feeling of disappointment, and even a determination to cling to the first story for the sheer pleasure of thinking your enemies are as bad as possible? If it is the second then it is, I am afraid, the first step in a process which, if followed to the end, will make us into devils.”
Lewis explains the way this happens. “You see, one is beginning to wish that black was a little blacker. If we give that wish its head, later on we shall wish to see grey as black, and then to see white itself as black. Finally we shall insist on seeing everything—God and our friends and ourselves included—as bad, and not be able to stop doing it: we shall be fixed for ever in a universe of pure hatred.”
Only part of the dynamic
I think he saw part of the dynamic, but not the whole thing. He may have explained much of the Alt Right and Antifa. He didn't see the normal temptation and why so many succumb to it. So many of us, genteel readers of works like Ethika Politika, and our friends. It’s much easier to speak viciously of others than Lewis describes.
Few people descend into the pure totalizing hatefulness Lewis describes. Perhaps the biggest reason most of us feel tempted to make our enemies look bad is that we want to make ourselves or our causes look good. We love something, perhaps something genuinely lovable but perhaps not, inordinately. We want to claim more for it than we can reasonably claim.
We're not usually tempted to the generalized hatred, or nihilism, he describes. I have known a few people who were and they were horrors to themselves as well as to others, the kind of self-enclosed people Lewis described so well in The Great Divorce. Most of us recognize the "Danger! Keep Out!" signs around that way of life.
We're tempted to hate the other as a way of loving ourselves and our causes. That makes the hatefulness and the exaggeration feel virtuous. And to most socially engaged Christians, painlessly acquired virtue is like catnip to a cat.
You're not a peevish, sour, angry little troll in his cave, hating the world. You’re not the frivolous worldly person shopping his way through life either. You're a warrior, a soldier charging into battle for king and country against the alien hordes. You expect your victory to cleanse the land of evil and your side’s victory to bring peace and justice.
That has its own characteristic dynamic that leads to its own kind of viciousness. You may start just wanting to promote your own side, and fair enough. At some point, you run out of superlatives. You can't make the thing you love look better. But you can always make the enemy look worse and in contrast your side look better.
You can report the enemy’s real sins, of course, but exaggerate them. And with just a twist or two, you can report even his virtues as sins. Do this day after day after day, and you will create for yourself and others an image of your enemy as a force of the most relentless, unremitting, unreconcilable evil. But you won’t know what you’ve done because you’ve never lost your sense of the good. Not being a troll will be taken as the sign of one who tells the truth.
That’s the main reason so much of Catholic social media has gotten so vicious. It’s not hatefulness but the effect of our deformed love of real good. You will also be tempted to expand your list of enemies, for pretty much the same reasons, but that’s another subject.