I can give a pretty straightforward explanation:
Before WW2 superheroes and pulp heroes were usually independent vigilantes, who might work with the police but usually spent just as much time fighting and avoiding them. They weren't afraid to slap a judge or a mayor around, and would kill thugs almost casually. A major theme of pre-WW2 superhero comics was some villain or another trying to embroil the U.S. in the continental wars.
WW2 changed all that. Superhero comics, in order to be allowed to be printed, were more or less forced to convert into propaganda rags for the American and British murderers. What economic pressure didn't do brain-dead statist ideology did.
Of course, the superheroes killed plenty of Nazis. It was after WW2 when the 'comics code authority' was implemented, essentially similar to the rating system of today; a ridiculous and arbitrary set of rules in order to keep the State from doing something even worse.
It is out of these two events - WW2 and the Comics Code Authority - that we get the superhero who cooperates with the police, has moderately left-wing/pro-democracy political views and doesn't kill people who clearly deserve it. This is also why almost every exception to the rule ends up being a supervillain (Supreme Power comes to mind).
It's so entrenched with the major players in the industry, along with the mainstream leftism that typifies most artists and writers in America or Europe, that it is pretty much impossible to expect a repeal before the copyright scam collapses. A few exceptions exist (Punisher being a noteworthy example), and these are more or less floating aberrations which are ignored by the cognitive dissonance which most people are expert at.
People with any real sense of morality will find this repulsive, of course. Socialist robbery schemes are robbery on a scale beyond that ever contemplated by Rhino. The unwillingness to judge politicians, police and thugs - fatally, if called for - is an abdication of reason and moral choice altogether. It is the unwillingness to face up to facts and reality and to treat vile scum as decent people. As Mr. A says, mercy to the guilty is always at the expense of the victim. Judge, and prepare to be judged.