A man who kills without reason cannot be reasoned with. — How to Train Your Dragon 2

The world is populated with good people.  For the most part, they want to make their way in the world, take care of their kids, and leave the rest of us alone.  They live in such a way that they don’t cause intentional harm to others.

But not everyone is like that.  There are those whose minds are so broken that they cause harm to others as part of their madness.  There are those who are so desperate that they choose to cause harm in order to get the things they need to survive.  And there are a few who cause harm just because they want to watch the rest of us suffer.

The insane can be either treated or sequestered so that they hurt no-one.  The desperate can be punished and then shown a way to get through life without needing to harm others.  As for those who hurt others for the fun of it, well, there really isn’t anything you can do to fix evil.  All you can do is protect against it and hunt it down when it rears its head.