I haven't seen the Movie yet.
Rudyard Kipling however answered your question of why...
"If any question why we died,
Tell them, because our fathers lied."
Kevin Tillman the brother of Pat Tillman wrote a moving and insightful piece (a poem really) in the same form as Kipling's "If".
Both Kipling's line, which was about WW1, and Kevin's essay are both contemporary and yet timeless I suggest each Republican chicken hawk read it.
http://www.truthdig.com/...tem/200601019_after_pats_birthday