You're talking about moral humans, here. Our soldiers/airmen/marines/sailors are not soulless automatons, nor are officers that develop strategy and provide direction. Nor would I consider their pay to be either incentive or motivation.
I'm sorry to break it to you, but there are immoral individuals in the US army, especially in the high ranks (where sociopath usually meet), like everywhere else.
If incentives are in place, nature will find the way even if you can't point to one single person who actually pulled the trigger.
A choice is being made in either case. Innocent people are being killed in either case.
Read this. Follow orders or get court marshalled. Its no surprise that after objections from pilots that they started singling out people who didn't give a shit about things like ethical objectives other than shooting their target accurately.