I didn't like "Flags" but you're comment about Vietnam vets is correct. I've got an older brother who is one, with a lot of battle decorations, and I've known and worked with a lot of vets who were in battle. None of them are head cases in fact most of them are saner and more productive than the non-Vietnam vets or non military vets from that era that I know.
From what I have read here - the odd thing is that Gagnion was the only one of the survivors NOT to show remorse for having been pulled away for a bond tour. Also, the late date of the photo and tour ARE part of the book, it was the last great bond tour of the war so to some degree it was non critical.