Yes, though true trolling is actually pretty rare. But yes, trolls try to completely disrupt an otherwise functioning forum by keeping a fake "discussion" going.
I was a professional gamer for a few years. You have peoples entire personas based on the fact they are good at getting people mad. Even happened at real life LANs too.
Oh yes, and then there are the griefers, who just want to make you sad, afraid and/or frustrated.
I do think trolls have gotten an undeservedly bad reputation because of being conflated with griefers. To me, trolling is relatively harmless attention-seeking vs. GamerGate, which is definitely griefing.
Some people may really do that, but whenever I see the troll label applied during a forum discussion it's usually because the "troll" is simply not agreeing with the rest of the hive.
Do people really do that?
I've been posting to newsgroups for 35 years...I have never once even considered betraying my personal beliefs just to make someone angry.
I guess that's why I struggle so hard with the whole "troll" meme.