They take pleasure in your pain.
Well, of course. It takes time and effort to be a troll. And it takes a bit of time and effort to get rid of them. That’s their sport: annoying you, trying to hurt you, and distracting you into the bargain.
I learned early in my internet experience—way way before I became a blogger—that there are online sadists. I observed one of them do his intensely destructive business on a website that dealt with various illnesses, a discussion board type thing.
I was there because of my arm injury. At the time (mid-90s), it was one of the few places I could find information about it and compare notes with other people who had a similar chronic problem. This troll terrorized people (and “terrorized” is not too extreme a word) who were in a different section of the forum, one that dealt with mental health problems. His m.o. was to befriend them, start a personal email correspondence with them and get them to bare their souls to him, and then after being helpful and kind for a long time—in some cases, years—slam them in an unmercifully abusive fashion and reveal the deepest secrets of their wounded hearts to others on the board.
The forum wasn’t properly patrolled at the time by its administrators, so a few of us set out to try to deal with the troll. Ultimately that campaign was successful, at least online: he was banned. But the destruction he had already done was incalculable.
And that’s why I have no trouble thinking that some trolls are sadists.
Not spambots, though. Spambots are helpful.