Haven't seen it in years, but it's not even really about Vietnam at all. The three-part structure is quite clear: It's a bunch of buddies and their lives in their hometown before the war, then all of a sudden some of the characters are in the middle of a terrible situation overseas (that really could be applied to any war), then the post-war ramifications (some people back home in Pittsburgh, and obviously what the Walken character gets up to).
Are you just against the fact that they'd portray Viet Cong as eager to make their prisoners play russian roulette (or that Saigon is shown as a Dionysian hellhole)? Seems more like a metaphor on war in general than anything pertaining to Vietnam itself. I just don't think any of it was meant to be a rumination on Vietnam War specifically... more of a study in terms of what happens to people before, during, and after they go to war. In fact, the ambiguity of Vietnam lends itself to a lot of movies like that.