But not for your ideological reason. It simply falsified some of the history.
1.
It misrepresents aspects of the military situation. The Japanese took
10 months to dig those caves and tunnels. It wasn't the relatively
last-minute tactical inspiration that the movie shows.
2. The
movie fails to give the viewer a geographical context for understanding the
progress of the battle. My recollection is that we see a map of the
island only once, briefly, somewhere near the beginning. Thereafter,
characters refer repeatedly to places we have no way to place in
relation to others. No, it was not meant as a training film. But good
directors find ways to give the audience the information it needs
without being pointedly didactic. Clint Eastwood, sometimes a superb
actor, has never been a good director.
3. The computer graphic of the invasion fleet offshore is embarrassingly obvious (as bad as some of mountains in the ridiculous The Lord of the Rings).
4.
The movie soft-pedals Imperial Army discipline. It shows one "bad"
lieutenant yelling at privates, but otherwise the officers act fairly
reasonably by American standards. In the real Japanese army, superiors
regularly struck inferiors (this was true at any level--a general could
strike a colonel, in front of his men). A Japanese private was not even
allowed to say "Yes, sir, I will carry out your order," because it
implied that the private was interpreting the order and expressing his
own intention to follow it. The correct form was for the private to
repeat the order word for word--"Do X, Y, Z, and return immediately,
sir!" The private was supposed to think of himself as a machine set in
motion by his superior.
5. The movie falsely portrays the Kempeitai as a strict police outfit that shot little kids' dogs. The Kempeitai was, in reality, the Japanese counterpart to the Gestapo, as committed to brutality against dissident Japanese, citizens of occupied nations, and prisoners of war, as Himmler's organization was.
You are right that the movie tends to
falsify the relationship between the two sides. I am not aware of any
Japanese abuse of captured Americans on Iwo Jima, but that was probably
only because almost no Americans fell into Japanese hands. Elsewhere,
the Japanese record on Allied prisoners was ghastly, and doubtless
American prisoners on Iwo would have been treated the same way had the
Japanese had the chance.
The single American Marine who kills a
Japanese prisoner in the film is made to seem, like the bad Japanese
lieutenant, an exception--when, in fact, Americans killing rather than
capturing Japanese was commonplace throughout the war. It simply wasn't
reported by American services or Allied correspondents. In general,
there was intense racial hatred between Americans and Japanese, and
that hatred was fully reflected in their conduct on the battlefield.
