So why is it ???

"The Cultural Defense of Hooty Croy On the night of July 17, 1978 dozens of police officers engaged in a gun battle with five Northern California Indians who had a single .22 rifle. More than a hundred shots were fired. Three Indians were wounded. A policeman was killed. 
After spending eight years on Death Row for first degree murder Patrick “Hooty” Croy, an Indian of Shasta-Karok descent was granted a retrial. His new defense team, headed by J. Tony Serra, argued Croy acted in self-defense and gave supporting evidence of the genocide against California Indians that has continued since the 1850’s. This strategy, known as a cultural defense, was used to explain why Croy feared for his life when he returned fire."

---http://www.shenandoahfilms.com/reasontofear-theculturaldefenseofhootycroy.aspx

So why is it no one seems to know the history of brutality in their own backyards?

The public schools teach Bury My Heart At Wounded Knee, while genocide in Northwestern California remains taboo.

People watch Lakota Woman & Pow-wow Highway for entertainment without doing anything to try and reverse the systematic oppression of native peoples everywhere- be it government enforced, or capitalism imposed; the creation of a go-road, or the subjegation of a race of people via boarding schools.

Liberals read native american spiritual biographies, while simultaneously not loving the marginalized drunken indians in their own backyards (and they don't even notice the irony).

Com'mon people!  We must educate ourselves.