Aside from the fringe human population that enjoy slitting hooker’s throats and bathing in their blood, most human beings have a deep aversion to killing. This poses a problem when one’s job requires them to kill (e.g. soldiers, police officers, CFOs). Conditioning people to kill and deal with the psychological consequences is known as Killology; a lovely neologism coined by Dave Grossman. He even wrote an uplifting book on the matter that I just added it to my Amazon Wish List.