I think part of the problem is that we're currently in a left wing dominated society as far as the goverment and media go. As a result those are the kinds of people that are getting attention, and being given platforms to express their theories seriously.
Bear with me here. I am quite aware most people on this site are aggressively left wing, where I am (well known) to be a bit more to the right than left. However in this case consider that modern liberalism is largely based on the idealogy of the 1960s and 1970s as defined by the baby boomers, and people like Mr. Non-violence himself Martin Luther King Jr. The "peace at any price" attitude very much prevails, as well as most generally masculine character traits such as aggression, and the simple idea of solving problems rationally as opposed to emotionally and morally, are in the decline. We're in the age of the "meterosexual" so to speak, where people have not only protested things like our war in The Middle East, but also volunteered to be "human shields" in the region to try and prevent our own troops from firing on the enemy. We also have entire organizations forming to go after any hint of violence, and being taken seriously enough where they try and take action rather than just pretending they are going to.... the group going after Mcdonalds for the super hero happy meals for example.
Consider that hippies, beatniks, and other groups are reknowned for their dislike of violence. That's the baby boomers, and they aren't out of power yet, despite selling out a lot of them still hold to those principles in the back of their minds. While younger folks are involved, I think current events in general (this, the mcdonalds incident, attacks on video games, etc...) are taking place because of unprecedented oppertunities the current goverment affords, combined with it being sort of a "last hurrah" for the aging boomers to make what they see as positive idealogical changes. I think as boomers are getting older a lot of them regret selling out, and tend to embrace the rhetoric that was more common in their youth now that they feel "established", safe, and a sense of mortality is setting in. I've run into a few sociological commentaries here and there.
As far as super heroes go, I will point out that the first pulp super heroes were VERY violent, and extremely lurid. This continued up until after World War II, and into the 50s to a large extent, many people argue that with the war gone the current generation was briefly seeking a way to define itself without something as overt as a war to provide the framework. Tales of violence and adventure were common then, and certain bits like "Nazi Dominatrixs" loosely bourne of stories about people like Ilsa Kochs began to proliferate. Some things I've read about the "comics code" have argued that it was the boomers who arguably started it, deciding to define themselves by being anti-war rather than through warfare. This lead to peacenik sentiments, and attacks on the comics as a violent brainwashing tool that would corrupt our children into monsters due to the visual aspects. Horror comics, crime comics, and war comics were all part of the justification for instituting the code, it was as a result of that code that the "super idealist" hero was born, along with things like the "code against killing" and the like, many existing characters were redefined according to those standards.
Another point for consideration is of course the ways the world itself has changed, today we are more aware of violent crime, and societal rebellion has become more direct. Not to mention long series of rulings that have made it more difficult to deal with what criminals are out there. Back during the 1960s things were a bit looser and it was a little easier to believe that say "Spider Man" could beat up a mugger and leave him tied up for the police and have that result in a happy ending. It wasn't accurate, but you could see it. Today we're more aware of how the system works, and also have to deal with draconian search and seizure laws and an absolute maze of precedents that allow criminals to plea their way out of serious crimes, or just walk away in general...
Movie Bob tried to make a comment on this in his recent review of "The Other Guys" where he talked about societal rebellion, and inadvertantly sort of made the other point. Back in the 1960s the "Rebels" were mostly hipster douchebag pacifists who attended loud rallies and smoked a lot of pot. There were some violent groups out there that people tend to forget about but they weren't all that common which is one of the reasons people tend to forget about that side of things. In comparison today's rebels like to go running around with guns and at least try and act intimidating. Kind of pointed out by Moviebob's point of showing a bunch of hippies showing the old rebels, and then some dude pointing a gun as the new ones, again that was always there to some extent (look at some of the things the Hell's Angels and other big biker gangs got into, there have been specials on it on TV) but today we hear about it in real time in the most sensationalized way possible.
Super Heroes have no longer been censored, and kind of gotten back to the crime busting attitude of guys like "The Shadow" (if not the same style). Due to the greater understanding of the reader base, the way things have changed in the world, better awareness of the extent of crime, and similar things (like a lot of older readers alongside the kids) you do indeed see a lot of violence and a take on things that is a lot more realistic to help with the suspension of disbelief in that "this could work, it could happen" that is needed for the reader to enjoy such fiction while they are reading it.
There is nothing negative about super heroes, their message, or their methods. I can see where the distinction between action heroes and the like is being blurred however, but it was always that way especially when dealing with the "blazing guns" pulp heros of the past. It does however go contrary to the agenda of a lot of very vocal people who think they need to protect us from ourselves.