Nazis certainly were evil at their core and may be an outlier. War though? It's difficult to not call war and it's atrocities evil. Even if you can prove irrefutably that you are on the "good side", two barracks down, the next town over, a 1000ft overhead something evil could be taking place specifically because war exists, and what's evil hides easiest in chaos and death.

Conflict happens. To the single soldier. The lonely wife. The stricken Mother and Father. War rarely has a true meaning. "Stand in the ashes of a trillion dead souls and ask the ghosts if honor matters. The silence is your answer" Javik (Mass Effect)

People tend to defend war because of their agreement or disagreement over the reason for a conflict. While there is often a morally right side and wrong side, all I really see are the lives lost.