I think it's a sense of personal impotence and a deep need to be heard by anyone willing to reply... and that's the key, eliciting a reaction.
I read somewhere that 40 million copies have been sold. Divide that by 13 (books published), that's 3,076,923 people on average who have bought the series, not to mention the hordes of people who have "borrowed" the books (friends, family etc).
So these trolls remind me of a joke: A mother, watching the passing parade, declares loudly: "Look! My little Johnny is the only one marching in time".
To all the little Johnnies who delight in trolling "the faithful": you'd have more luck converting devout Christians to Satanism than having 3 or 4 million WOT readers decide, based on the rantings of a few very ineloquent trolls, that they wasted 22 years of their life.
In short; the good people on the WWW have come to see trolls as the joke they are... yes amusing and somewhat annoying having to deal with such pitiable fools, who obviously think their repetitive screeching is changing the world or whatever it is they derive their jollies from.