Evil, in its purest form, is dispassionate, while evil fired by passion is self limiting because passion, waxes, peaks and then ebbs. This constrains the carnage it can create.
Dispassionate evil has no such constraint. It can go on and on because it is set into motion by bureaucrats, technicians and policymakers.
In the beginning, Hitler’s Final Solution depended on death squads who interacted personally with their victims. The executioners started going psycho on the high command, and they couldn’t produce the numbers. It was deemed too inefficient.
So the technocrats were brought in. They drew up blueprints and let contracts for construction of the death camps; they inked contracts for the delivery of the poison gas and rerouted the trains to deliver their cargo to the camps. It was only when the Holocaust transitioned from passion to policy that it got the numbers it needed.
War increased its viciousness with the entry of technocrats. Former Secretary of Defense Robert McNamara got his start plotting targets for General Curtis Lemay, the mother of all fire bombers. The technocrats designed new and bigger weapons; it was their genius that gave the world napalm.
During the war, policy wonks reasoned that it could be won by bombing civilians. As a result, World War II became the first war in history in which civilian casualties were greater than military casualties.
Dispassionate evil is perpetrated by the most pleasant of people, many of whom go to church every Sunday and keep their suburban yards immaculate. They love their children and their wives, are civic minded and have never seen a dead body.
By every psychological measurement, they are well-adjusted.
In modern times, the Devil wears Dockers™.