Well, you can look at it in a handful of ways. For example the changing way comics are written and regarded by the public. (GENERALLY!) Superhero comics used to be regarded as something for children. They were positive, classic tales about heroes and villains, good defeating evil. Clark was originally the sort of bright-eyed boy who would thrive on that sort of entertainment. Eventually the readers were expected to leave their comics behind and move onto something more nuanced and mature. Adults could and did read them, but they weren't thought of as serious stories worthy of much thought. Clark was to be a Peter Pan character, the eternal child, enjoying things meant for children in an wholly innocent and pure way.
But the perception of comics changed as comics themselves did, and the stereotype of the comic fan evolved as a result. Comics often attempt (and fail) to be taken seriously by appealing to base appetites, such as sex and violence. Of course most people understand that sort of thing is actually immature, sophomoric even. It pretends to be 'grown up,' but is actually devoid of any real depth or creativity, hence why the comic fan is often thought of as basement dwelling manchild, drooling over consequence free violence and girls in skintight costumes. From a cynical perspective it is rather fitting that Prime has changed from idealistic and positive young boy to someone who is all about the gratuitous violence and who takes on adult problems with the maturity of a much younger individual.
There's also a reasonably valid point about fan culture and the internet there. Not just comics, but fandom in general. The greatest fans of something are often the ones who complain the loudest, taking their entertainment perhaps a little bit too seriously and posting their hyperbolic comments across the web. The book Planet Simpson had a chapter on the very subject, pointing out that even during The Simpsons' 'golden age' the fan community used the (at that time) fledgling internet to complain about it, tearing each new episode to shreds as it aired. This was their favorite show, a show that (at the time) was almost indisputably the cleverest and best written show on television, and they were constantly bitching about it! Every fandom has such individuals. Comic fans are an impassioned lot, which isn't a bad thing. I think it suggests a kind of love and vigilant care for the medium that is genuinely touching, I am an angry comic book fan too, after all. However to an outsider, or to the writers who often receive harsh criticism (which is cool) and hateful insults (not so cool), it can seem a little strange. Prime seems to be one of those hateful, self important comic fans you often encounter on the web.
I think it's a little funny that Johns created such a character, considering he's known for pandering to the sex and violence (particularly violence!) crowd with his writing, and really he's just an overgrown fan himself. I do question the appropriateness of him teasing the fans like this, it's as obvious as when the The Simpsons took a shot at their fans in the 'Itchy & Scratchy & Poochie Show' episode (""Why would a man whose shirt says 'Genius at Work" spend all his time watching a children's cartoon show?"), but slightly less endearing, since there's also an element of 'Nyah, nyah, this is what you sound like!' to it. I do like to think there's some self mockery going on there, just like I think Zoom was a self aware creation on Johns' part, but I may be giving him too much credit.
(Of course for Prime's transformation to be truly apt we'd have to assume that comic fans were not so 'combative' and negative previously, but that's near impossible to judge. Even the letter columns can't be trusted, since I don't doubt that the big two were willing to filter out a lot of the more negative letters.)