Earlier quoted context omitted.
Whatever you think might be going on with the overall discipline of the US military today, it has nothing on how bad things were in the Vietnam era. Enlisted men slipping grenades into their officers’ tents after getting high as a kite in a combat zone was a regular occurrence. https://en.m.wikipedia.org/wiki/Fragging This comment just shows you to be ignorant and contrarian.
Fragging was more often a rational act of self preservation than drug-induced madness. It was mostly soldiers getting rid of officers who were likely to get them killed. Heroin and weed don't just turn otherwise good men into murderers.
And recent research absolutely has shown that heavy cannabis usage in adolescence and early adulthood does have a clear association with an increased risk of developing psychosis and schizophrenia. Just because the war on drugs lied about the effects of less harmful drugs like cannabis doesn’t mean they can’t be hazardous to your health like any other substance.
Regarding heroin - one may not be particularly murderous while zonked out, but addiction can make people surprisingly aggressive.
I’d also like to add that the company-grade officers stuck in the mud alongside enlisted were less at fault for the needless deaths than the incompetent general staff or the political actors who got us and kept us over there in the first place. You might enj the novel “Matterhorn” by Karl Marlantes, a Marine infantry officer who served with distinction in Vietnam. Or you might prefer “Dereliction of Duty” by Lt General H.R. McMaster, a renowned commander of the GWOT era who wrote his PhD thesis on the failures of Westmoreland and the other generals who mangled Vietnam.