While using a somehow poisonous defoliant against crops and forests is certainly less atrocious than using a certainly lethal Zyklon-B directly against humans, destoying 85% of the crops is also somehow irresponsible.

All wars are bad things, purportedly waged to avoid even worse things. But the Vietnam War had something especially bad about it, probably that same feature that made the US fight for 10 years, ruin the country it tried to protect, and effectively lose the case. One thing I remember from a historical book about that war is a general saying (approximately) "Do you think we will change the entire way our military functions just to win a frigging war?".

This kind of mindset definitely leads to both atrocities and losing. NB: applies to project management in general.