I don't write well on this issue, because I'm utterly unable to muster any shred of sympathy for the views of the other side. (Readers seeking intelligent commentary would do well to chech out Moira Breen's thoughts on the subject.) I can only conclude that our opponents' steadfast desire for ignorance stems from a deep spiritual insecurity and doubt as to their beliefs' viability in the modern world. When a belief system can no longer react to scientific or cultural changes, it is dead; the die-hard believers may still commune in their cloisters with the ghost of their faith, but it provides neither comfort nor ethical guidance to the laity. A faith which shuns science is shunning reality, and is therefore of little relevance to the world its believers must inhabit. If Native Americans want their culture to remain an inviolate museum piece, fit only for the contemplation of tourists red and white, that is easily achievable. If they want a culture which will actually define the lives of future generations and provide them with surprise and inspiration, then they need to study Kennewick Man, and see what they discover about themselves.
Digression: I think that this phobia that any interaction with modern reality will destroy their culture is also responsible for the disappointing lack of creativity in the Native American music scene. The only alternatives to traditional drumming, chanting, and fluting seem to be generic rock with 'Red-Power' lyrics, or equally bland New-Age/Dance-club synthesizer-techno washes. I have certainly not heard anything on the level of the neo-tribal music coming out of Eurasia (check out the Saami and Tuvans, for instance), in which traditional techniques and modern sounds interact very agressively and creatively.
Thanks to Chas Clifton for the Kennewick-related links.