Anyone can become a troll. Studies
show most Internet trolls are otherwise
reasonable people who’ve never trolled
before. If you’re already in a bad mood
when you stumble upon a troll post,
you’re twice as likely to turn into a troll
yourself, regardless of your history
of online behavior.
Basically, one person not controlling their cranky can spark a vicious cycle of creating new trolls, who then create even more trolls, who, in turn, continue to multiply like bunnies.