I think McLuhan was very insightful in the ways that comics work, particularly the idea that because comics are told in still pictures, like a novel, it requires mental power to read over. Many people that don't see the big picture blame all sorts of picayune little straw men when explaining why comics don't sell as much as they used to: continuity, the overabundance of superheroes, the fact that comic book store owners all resemble that Simpsons character, etc. The reality is, comics are a medium that. in contrast with television and movies, require imagination to work, just like novels and radio - and why use your imagination when you can rent the video?
In his first book, 1951's The Mechanical Bride, McLuhan reproached the Man of Steel, calling Superman's crime-fighting tactics "the strong-arm totalitarian methods of the immature and barbaric mind."
My first instinct is to disagree with McLuhan's statement here, but thinking it over, there's pleasure to be gained in great visceral feats and barbaric brawls; this is the whole point of Superman and superheroes. My enjoyment of superhero comics is inherently immature for that reason. The savage violence, destruction, and mayhem in comics is fun and rather childish; adults understand that people can really get hurt in fights and it really doesn't solve anything ("Hey, put down that crane, you'll take somebody's eye out with that!"). McLuhan's not wrong - but he's missing the point.
Many write of Superman in praise of his decency and honesty, and while these characteristics are important to who he is, what also is important is the fact he is an adventure character in adventure stories, an "Ace of Action" whose main franchise is beating up people whose behavior he disapproves of. Superman is a fictional character and so we can enjoy his behavior from a vicarious perspective that would be different from someone in say, Superman's own world.
I've always loved the dichotomy of how Wonder Woman is supposed to be a pacifist but somehow she always lays a few knockout punches in her stories. Sure, all that pacifism stuff is all well and good, but this is a comic book story, so dammit - we expect her to throw down and chuck a couple tanks while she's at it, too!