Quite true. Unfortunately, given the history and prehistory of other human groups, this doesn't mean they were peaceful.
I highly recommend War before Civilization: The Myth of the Peaceful Savage by Laurence Keeley.
http://www.amazon.com/War-Before-Civilization-Peaceful-Savage/dp/0195119126
The author compiles what is known of "primitive" cultures from archaeology, anthropology and early explorers. What he found is that the vast majority of such societies had a much higher death rate from war than more modern "civilized" societies.
For example, the 20th century is often called the most violent century in human history, with an estimated 100 to 200 million people killed in its wars. If the average death rate from warfare from the dozens of primitive societies he studied had applied worldwide during the 20th century, 2 billion people would have died.
And that's just the average war death rate of primitive societies. Some were much more warlike than the average.
This really shouldn't surprise us much. Let's assume Tribe A was peaceful and warlike Tribe B moved in next door. Either Tribe A quickly became warlike in self-defense or it quickly became extinct. The book documents numerous examples of this extinction, BTW.
I'm suffer under no illusions about the Indians. I really don't care about the Indians. But there are just little BS flags that go off in me once in a while. When you read about Lewis and Clark, they want you only to learn about Lewis and Clark, but I guess I pay attention to everything; and their interaction with the Indians was one of those things. I've also driven around this country. Before that though, in the 50s one day when my father took me to a baseball game at the Polo Grounds, my father drove me around Harlem to show me "where the poor people live." Well, when I did that drive around the country, I went to New Mexico. And there I saw Indians living on land "we" "gave" them. The "reservations." No water. Nothing grows. Miles from anything useful. You see their cars and you wonder how they can get to anyplace they might want to go without a breakdown, or three. It's the closest thing we have to third world poverty that I have seen in this country; and all those folks in Harlem ought to be taken out to those reservations in New Mexico so they can see how lucky they are.
ML/NJ