According to this man's own article, Eastwood's film features a "sadistic Bushido-oriented captain," and apparently pits the film's Kuribayashi character into conflict with his junior officers who are much the same. I don't see the relevance of this fellow complaining that Eastwood's Iwo Jima film doesn't depict incidents that happened in Nanking or Unit 731.
The outrage seems feigned, anyway, since even this guy writes that "Sure, all grunts are similar in that they miss their homes, their wives and sweethearts, they look at photographs of them before the battle, they tell jokes and form friendships, they are kind to little children and dogs."
It seems to me that that's all Eastwood was aiming to show, and if a fine film like Das Boot can be made about soldiers from Nazi Germany without shaking our confidence that there was "any point to us opposing them", then our tender minds should be able to survive Letters from Iwo Jima.
Actually, Das Boot was about sailors (specifically submariners) not soldiers.