One possibility is that it's a byproduct of the school system. Most of us spent years at each other's throats in a Lord of the Flies type environment, so it's natural for this behavior to transfer to the internet.
I think it's probably a fine line, but there are "trollish" comments that can be made that aren't even disingenuous, never mind nasty or negative.
The so called old school trolling wasn't about disruptive behavior, it was about getting people to consider thoughts that they aren't necessarily comfortable with. And not necessarily uncomfortable in a dark or disturbing way.
You are shifting the perspective here. Trolling in your sense, as a weak and vile but effective antisocial interaction would be significantly characterized by lacking better traits. Either it's institutional or school can't help with it. This is one of the things school tries to control for, so, if they can't control it, then because it's not from within their institution. Either way you can't just say that without any argument. I don't accept the irony that is mentioning the mandatory literature as an argument.
Since that topic is controversial and the tone mocking, I consider it flame bait. Did you enjoy writing this?