Trolling is amusing to me. One, because of the person doing it. Either they're really good at it, which can make it enjoyable, or they're just plain bad, which makes it amusing.
Two, because of other people's reactions. EVERY GAME IN EXISTENCE NOWADAYS HAS A MUTE/IGNORE BUTTON. Yet nobody uses it if there's a troll. And more often than not, the player will admit to knowing that the person is a troll. Yet they fail the golden rule of dealing with trolls: don't feed the troll. And that's just amusing as hell for me.