What is being called trolling here is inherent to web based discussions, and pretty much all moderated discussions. The reason it is inherent is that there cannot be an objective definition of trolling (or, to use web forum terminology, offensive posts) that is meaningful. It is inherently subjective, and to be enforced, there must be enforcers, i.e., moderators. And moderators are a biased as anybody - and everybody is - and the moment there is more than one moderator, the "trolls" will play them off against each other.
What you end up with, and I've seen this every single time in every single forum, no matter how lightly or heavily it is supposed to be moderated, is that people the moderators like - those who suck up to the mods - are allowed to do things that people the mods don't like. Every. Single. Time..
I saw a guy in one forum banned for refusing to say something that would have gotten him banned - the mod acknowledged this in the post announcing the ban. I've gotten an account suspended for reporting offensive behavior (by one of the mod's bootlickers) in exactly the say that mod had told me to do.
This isn't a problem with web forums, though. It's a problem with human nature. You get a group of people over a certain size, it will fragment in to cliques, and they will come in to conflict with each other. That's how people are. So any attempt to create an online forum with no trolls is either a pie-in-the-sky fantasy by someone without a clue, or it's pure snake oil. Either way, it's doom to fail, fail, fail, and then fail some more.