A soldier committing a crime is still a criminal
A soldier committing a war crime is, sure. A soldier killing another soldier (authorized by his country) is most certainly not. There are treaties that recognize that face.
t goes against basic decency
I live in the real world where governments are endowed with the ability to do a lot of things we don't allow individuals to do. Use deadly force without facing eminent harm, for instance. Intelligence services tend to save more lives than they cost. When you look at a real war, they are important as troops. But they cannot be deployed as easily. They already have to be in place (to a large degree).
Also, I'm not sure what the common decency argument is supposed to mean. I tend to think it violates common decency to take pictures with someone else in the background an upload them to Facebook, yet people do it all the time. Why is this crowdsourced panopticon okay, but a concentrated one not?