Reminds me of a bit from the comedian Tim Wilson, when he sees a hitchhiker he wants to just pull over out of sheer curiosity and ask "Have you not seen the movie?!"
Same question for these people...have they not seen the movie?! Take your pick, autonomous killing machines ain't exactly new material. The possibility of their becoming self-motivated is bad enough, if unlikely. They're plenty bad even without learning to think for themselves. Sure, the military will cite having them because they can do things without risking a human life, they can go places a human can't go, but the real reason they want them is because they will do what they're programmed to do -- to quote Alien -- "unclouded by conscience, remorse, or delusions of morality".
Human soldiers reach points where they refuse to continue following orders. Machines don't. That's why they want them. When they want to massacre American civilians they don't want any mutinies on their hands.