Another reason while in war you avoid moral ambiguity.
To keep the morally ambiguous from making stupid and dangerous decisions. The continuous focus on the evils of America in this war, along with the drumbeat against our leadership only makes it more likely that weak and stupid people will decide they should in fact be helping the enemy. In Vietham it led to rich and privelaged people like Jane Fonda and John Kerry to despise our country and in her case actively support the enemy, and in his case to toss away his medals (which magically came back).
Ed