No, that's true, and I don't actually think that the world is divided into good and evil. Nor do I think anyone doing this really has anything to fear from the justice system.
But to the degree you can take a normal person and twist them into something horribly unfit for civil society, having them do torture is the way. It's the express lane to not seeing others as human, not even when they're in front of you, being tortured by you.
The world has to modes: In one mode, we need people, as much as we can get, to make something bigger out of this world. In another mode, the world can no longer grow, so we divide, we conquer "the others" or be conquered.
The definition of the word "evil" changes depends on which mode we are in.
That's why Niccolò Machiavelli suggested that it is useful to be both loved and feared, it gives you the best chance when a challenge is facing you.
