I enjoyed the series but it was a guilty pleasure to some extent. I do not doubt that the things the Marines did in the movie occurred, but the Japanese were brutal and sadistic also.
My problem is that I only remember 2 things in the movie that the Japanese soldiers did that were really bad IIRC - tying a yank to a tree to be victimized by our own shelling, and using civilians as human shields in an attack.
The Yanks on the other hand had multiple atrocities in every combat episode, including killing kids and steeling gold from dead persons mouths.
A person with little knowledge of history would think " Japanese were mean, but they are not totally racist sadistic monsters like us."
WW I usually agree with you, but I disagree on one point: PC has changed lately, showing Americans as racist sadists has become PC - Showing our enemies that way is what is not PC (see media response to Abu Graib vs. beheadings of American prisoners).