I saw the movie the other day and while I was never a Marine I was in the Navy. I can't speak about the specific battle scenes or Marine temperment however, the feelings it describes are, in my opinion, accurate.
The movie and book I presume, are not necessarily about the actions of the Marine Corp during that period but more about how the author felt about what he was doing. I can remember thinking some of the exact thoughts he had regarding infidelity, bordom, and loneliness. The author is mearly expressing how he felt, not bashing anything.