People with nothing to lose. A good friend, who was a psychiatric nurse, taught me never argue or fight with a person with nothing to lose. There are more than a few in the wold, unfortunately.

More common is anonymous people on the net who threaten to do so. My point is a bot is predictable, but humans are emotional and irrational. Further, you can't always tell the difference between the snakes and the monsters in an anonymous environment (notice I'm not anonymous). Thus, I'd be more willing to argue with a bot.