Earlier quoted context omitted.
It is probably easier to get pilots to bomb civilians with a Playstation controller in what looks and feels like a video game, than an actual person present.
It's not a question of "ease". Military pilots take orders; COs tell them how high to jump, and that's what they do. Either they follow orders or they are relieved of duty (and possibly face court martial). Some drones are operated by a division of the CIA and are out of military control, however. This is probably the most worrisome aspect of the program. However, as long as 99% of their targets are bad guys, America…
Even so, and despite all the training, some do refuse orders. They're also at least theoretically obliged to refuse illegal orders (i.e. war crimes), at least in my country.