I don't know any trolls personally but I  think I may met some inadvertently over the years. My kids all played minor hockey and when the  internet started going full blast about 1995, there were forums on their respective teams. The comments about the players , coaches and even the mothers on the teams was not very complimentary. Of course everybody posted anonymously, and some of the things said about the kids (male and female ) was downright criminal. 
Years later one of my son's was signed by an NHL team to an entry level contract and one of the assistant general managers on the NHL team actually quoted a personal slight about my son that he had read online. Suffice to say my son had a nice career but the damage had been done.  He went overseas and all of that crap vanished. 
The internet, because of people's anonymity is sometimes a cesspool of logic. Things we wouldn't say to stranger's faces are often brazenly posted online. I can see why online newspapers choose no forums.