George Orwell, in his essay "Raffles and Miss Blandish":
... what is now fashionable to call ‘realism’, meaning the doctrine that might is right. The growth of ‘realism’ has been the great feature of the intellectual history of our own age. Why this should be so is a complicated question. The interconnexion between sadism, masochism, success-worship, power-worship, nationalism, and totalitarianism is a huge subject whose edges have barely been scratched, and even to mention it is considered somewhat indelicate. ... It is important to notice that the cult of power tends to be mixed up with a love of cruelty and wickedness for their own sakes.
The presence in popular culture of all the things Orwell touched on in that list often passes without direct commentary, in big part because it's just so commonplace, and because a society's greatest madness tends to be invisible to itself. We don't think about the fascist undertones of, say, most superhero stories or the jut-jawed brand of military-porn SF. But that doesn't make us all closet fascists; it just means that we aren't always aware of how an unhealthy social message can be easily smuggled into our entertainments when we're not looking. And sometimes it happens when we are looking, and we shrug it off.
(Digression. One of the theories I have heard floated about DC vs. Marvel is that the latter franchise is the more self-conscious of the two about power and responsibility, while the former is more freely heedless of such things, but I'll leave further discussion of that to people more familiar with both.)
This passage, though, I found even more striking:
... [the book] has not the smallest connexion with politics and very little with social or economic problems. It has merely the same relation to Fascism as, say Trollope's novels have to nineteenth-century capitalism. It is a daydream appropriate to a totalitarian age. In his imagined world of gangsters Chase is presenting, as it were, a distilled version of the modern political scene, in which such things as mass bombing of civilians, the use of hostages, torture to obtain confessions, secret prisons, execution without trial, floggings with rubber truncheons, drownings in cesspools, systematic falsification of records and statistics, treachery, bribery, and quislingism are normal and morally neutral, even admirable when they are done in a large and bold way. The average man is not directly interested in politics, and when he reads, he wants the current struggles of the world to be translated into a simple story about individuals. He can take an interest in Slim and Fenner as he could not in the G.P.U. and the Gestapo.
The line about "admirable when they are done in a large and bold way" made me think again of comics, and also, again, of military SF. Both revel, in their own ways, in violence being the only truly dramatically satisfying way to deal with a problem.
That said, there's a profound difference between a) violence as a last resort, used with great trepidation and care, and followed up with a postmortem of motives and behavior, and b) killing 'em all and letting God sort 'em out because it makes for a better story to tell ourselves. I don't just mean "story" in the sense of "fiction", either. I also mean in the sense of "social myth", the one where we were on the right side all along and we never had to think too hard about who to shoot.
To say that the violence can exist outside of such a context is to tell ourselves a reassuring myth about violence, to buy that much more into all the ways we can insulate ourselves from it. It is not overexposure that causes desensitization; it is lies, especially casual lies, about the nature of what we are being exposed to. I don't worry about the man who plays a thousand hours of Grand Theft Auto and doesn't take it seriously; I worry about the man who watches a thousand hours of news and doesn't take that seriously.
I should point out that I don't consider myself immune from attempting to invoke any of these things. One hardly needs to pick through my work with tweezers and sieve to find action scenes. But I'd like to think there's a difference between the mere presence of such material, and its use as a nod-and-wink to the worship of power — yes, even if I haven't been able to master such a distinction in my own work.