The way to deal with a troll depends on the aim of the troll. Like the good doctor said, most are young dumb and bored, but some are more malicious. For the smarter ones, ignoring them tends to work. They want people to bite into their bullshit, if you don't give them the satisfaction they bore and move on... or switch to more actionable activities (spamming, whatnot). If they do the latter, report them and call a mod. Be aware that even if you don't bit on their topic, they will try to trigger you by twisting your words. Start a real conversation with others in the room, mute the troll, eventually they'll bail. Most important thing when dealing with any troll, don't let them get you angry. It's EXACTLY what they want. If they get to you, they win.