Any community, whether online or not, is made up of people. And people are diverse with many different opinions, including what they believe to be “right” and “wrong.” There are individuals who are so different from the “normal” group, so radical that their idea of “right” is nearly everyone else’s idea of “wrong.”
They are rare. But the larger your community, the bigger chance you have of encountering one of these “anomalies” in any community. In a small community where everyone knows each other (say a close-knit neighbourhood or a small guild/forum online), the moderation is usually self-contained. Neighbours will prevent the outlier from tarnishing their community, many times without involving the police. Likewise, the guild/forum will usually handle the outlier without an admin-level moderator.