The human mind is designed to deal with either/or’s, with duality. Clean/unclean; safe/unsafe; move/stay put.
It occurs to me that what we call evil is actually best understood as a natural energy taken too far. Evil is a healthy expression of self, of individuality, taken to the point where it is unhealthy. It can be very useful to be cruel to oneself at times, but almost never to others. But not never. Physical Therapists, and drill instructors have to be mean to get people past their self imposed and inaccurate limitations.
But if we are all cows, doing emotional grazing, there is a circle within which the grass is green and healthy and nourishing. Only if we stray beyond that circle does it involve us in manias, drain us of happiness and emotional wealth, and cause us to want more the more we eat.