People seem to have an easier time forgiving crimes if they're highly abstracted. I'm not sure if this is apocryphal but apparently drone pilots are less likely than other soldiers to feel extreme guilt about killing people. Prince Harry flew a helicopter in action and compared it to a video game, likely a PR recruiting statement but revealing nonetheless. I'm not a soldier so am speaking out of turn and may be completely off base.
IIRC I read some similar research as well - not only about drones, but also in general that most casualties are made by "fire and kill" weapons like artilery and air power mostly due to how soldiers tend to avoid killing other people unless prepared psychologically.
