Normally watching videos is also a no go for me but this one was informative and the images were needed to flesh out the information.
Something that I remember well was that the Vietnam war produced not just combat veterans but especially among the green berets were some cold stone killers, at Tigerland you could see it in some of the Special Forces older guys with their jungle formed slender bodies and black dead eyes and nothing but no nonsense intensity, the majority were normal combat vets, but on a few, it really showed.
Fortunately, I never had to experience the war. I considered going into the miltary, but never did. But I certainly can understand why some of them who returned certainly had theat expresion of which you described. I never, ever, hated those people who went to that conflict. I stood with them and their call toduty
I hated those who hated them.
My father & grandfather both were involved in WWII. My father in Italy, and my grandfather in Germany. Neither one offered up their experiences, and my inquires were limited to be sure because of that.