Dad gave many years to the USA, and his son almost certainly followed in his father's footsteps. Can you blame him for being angry at the way he perceives his dying son was treated? An unfortunate situation, all the way around.
That said, I have mixed feelings on this, as part of me believes that the parents are being exploited by those who feel "we should not be there".
While the parents are concerned over the treatment of their son, I noticed it took a neighbor to contact the parents to notify them of the problem. I don't know how often you talk to your folks, or your wife, but neither of them considered it strange that he didn't call. But I suppose it's the Army's fault either way...