The mass executions — intended to keep possible southern leftists from reinforcing the northerners — were carried out over mere weeks and were largely hidden from history for a half-century.
You know, maybe I'm just an asshole, but it seems to me that when your country is being invaded, rounding up enemy sympathizers and neutralizing them to prevent a guerrilla war behind your lines is a pretty necessary action. Not preferable, but necessary.
I fail to see a problem with this...
Had the United States actually been invaded by a large hostile force in 1941, you can bet your ass that FDR would have given the order to ventilate as many Japanese and Nazi sympathizers as he could.