We Have Met The Enemy
And he is us.
They are not misfits or sociopaths. They are people who find it fulfilling to kill us and destroy our society. As time passes, we will meet more and more of them. And, in the fullness of time, we will remember that Machiavelli warned us half a millennium ago that "man is more inclined to do evil than to do good," and that the primary role of statesmen and other leaders is to contain the dark forces of human nature. Evil cannot be "fixed" by some social program or suitably energetic public-affairs strategy, or by "reaching out" to our misguided comrades. It must be dominated.