Collateral damage is one thing, brutal execution is something else.

You are right that this is probably not the worst thing they did. I’m absolutely sure the US armed forces are a highly sought playground for psychopaths and people with sadistic tendencies. Furthermore military tends to attract people with a predisposition for authoritarian and/or facist mindset. We saw the snapshots of unspeakable torture - made by people that were so entertained by the atrocities that they just had to make commemorative pictures of it.

But collateral damage is something else: if I blow up a house with a terrorist leader in it, weil the debris kill a bystander? It happens in every war and it’s the main reason why a ‘just war’ still can’t be fought without tainting conscience.