That's interesting, I saw a documentary recently on two chimp tribes/families in Africa. One tribe lived in a piece of forest that was ever shrinking due to man's influence, clearing etc. the other tribe lived in a untouched wilderness with no limitations on their territory and no stresses from man, a really natural environment.
The first group in the limited and stressful territory were crazed and violent creatures who killed a human baby, killed their own babies and other primates in the forest in lustful and violent frenzies! The second group in the natural environment were peaceful and harmonious, they would not eat foods offered to them by humans (unlike the other tribe who were addicted to such offerings) and they did not kill eachother or other animals in the forest. I think this says a lot about why we or they eat meat. The movie you saw reminded me of it.