I think terms such as "War Criminal" and "Crimes against humanity" are highly dependent upon whether or not you are in a position of power.
We like to think we are objective, but as has been pointed out, the difference between Heroes and "War Criminals" is whether or not their side won the war.
No, hardly, and for examples, consider German Generals Rommel and Von Manstein -- both admired by their enemies and never accused of war crimes.
In the US Civil War, the same can be said of Generals Lee & Jackson, amongst others.
The charge of "war crimes" requires particularly heinous actions, of which our Civil War was remarkably free.
Yes, there were some "war crimes" committed, but in comparison to other wars at other times, remarkably few, imho.