Who is really to blame for collateral damage?
The reason there is collateral damage is because those who want to make war -- the people who blow up women and children at an Easter celebration, to give just the most recent example -- have intentionally chosen civilians as their targets. They intentionally hide their soldiers and their weapons inside peaceful places such as hospitals and neighborhood markets, forcing those who try to stop them to risk hurting the innocent. They do this cynically and deliberately.
They are ultimately to blame for collateral damage. They are those who force the military to choose between letting someone blow up 70 civilians, or to possibly kill 1 civilian in trying to stop them. There is no possible justification for intentionally killing civilians, but it is justified to try and stop these evil aggressors, and to target them and them only as much as possible.
One thing the movie draws out to great effect is the supreme difficulty of conducting war not only remotely by drone, but also remotely by committee. There you are, sitting on the can because you have food poisioning, and someone hands you a cellphone and asks you to approve the killing of a terrorist. It's an impossible question, almost absurd. You cannot conduct war by committee. I'm sure many Britons are comforted by the idea that the chain of decision goes all the way up to the Prime Minister (in real time!), but I was personally horrified. You need to figure out the rules of engagement BEFORE you even get into battle. You can't ask soldiers to put their lives on the line while you call up the phone tree. The Americans look cold by comparison in the movie, but in fact I think they had the better of it. You make your choices and then live with them.
A very thought-provoking movie.