Everyone: "It seems we, as humans, have a pretty strong dislike of executing other humans. A biological aversion to commiting genocide, one might say."

Nazis: "Halten Sie mein Bier!"

But in all seriousness, your comment reminded me of "The Banality of Evil".

For when I speak of the banality of evil, I do so only on the strictly factual level, pointing to a phenomenon which stared one in the face at the trial. Eichmann was not Iago and not Macbeth, and nothing would have been farther from his mind than to determine with Richard III 'to prove a villain.' Except for an extraordinary diligence in looking out for his personal advancement, he had no motives at all… He merely, to put the matter colloquially, never realized what he was doing… It was sheer thoughtlessness—something by no means identical with stupidity—that predisposed him to become one of the greatest criminals of that period. And if this is 'banal' and even funny, if with the best will in the world one cannot extract any diabolical or demonic profundity from Eichmann, this is still far from calling it commonplace… That such remoteness from reality and such thoughtlessness can wreak more havoc than all the evil instincts taken together which, perhaps, are inherent in man—that was, in fact, the lesson one could learn in Jerusalem.

— Hannah Arendt, Eichmann in Jerusalem: A Report on the Banality of Evil