Here's some stuff I wrote in the thread Lonesome EJ mentioned up there:

Being brave doesn't mean you aren't doing wicked things; people who do wickwed things aren't necessarily cowards.

It's just that we tend to throw the word coward at people who do something horrible, because it's one of the most powwerful insults we can think of when directed against an enemy. So you get absurd things like Clinton the other day denouncing the suicide bombers in Yemen as "cowards" -which is the one thing you can't reasonably say about a suicide bomber.

The very same Nazis who carried out appalling atrocities were often insanely brave themselves when it came to combat. I am sure the same went for many of the US Cavalry who did the same kind of things as the Nazis, back in the 19th century.

There are different types of courage. Refusing to obey orders you know are wrong is one of the highest forms. I suppose you could on that basis argue that soldiers involved in massacres and atrocities are cowards by definition, unless they actually believe what they are doing is right. Which I imagine few of them do.

The thing is you can be brave in one situation on one day, and cowardly in another situation on another day. That's why using labels like "coward" or for that matter "hero" for people rather than for the things they do is misleading.