I think viewing whites who adopt the trappings of Rastafari with a bit of healthy suspicion is more than justified given the ongoing history between Black and white on this earth.
But if the principles of Rastafari relate to Native peoples who are not [directly] African, I see nothing at all wrong with that. The only problem I might have with that is if it eclipses their own traditions which they should maintain. In many cases though I think a good balance is achieved.
We have Amerindian and East Indian Rastas in Guyana. Me nuh see nothing wrong with that. We probably got Chinee and Puhtugee Rasta too, me ain' know.
The Rasta emphasis on nature would appeal to folks who already live a natural way of life, or who would like to recapture the natural way of life they once lived.
The Rasta emphasis on equal rights and justice would appeal to folks who are downpressed and dispossessed. (And speaking for my country, no one is lower on the social scale than the Amerindians.)
East Indian Rastas in my country are making a progressive move because they are rejecting the racist ideology held by many (not all) Hindus there, that the African is inferior. They are identifying with the African without necessarily discarding their own roots. (Remember there were East Indian Rastas from the very beginning, one of Leonard Howell's right hand men was a coolie bannah.)
Rastafari is a way of life created for the most part by Africans and focused on Africa, yet it carries with it universal principles applicable to anyone. And as I said it has a special resonance for the dispossessed Native peoples of the earth, whether African, Amerindian, Pacific Islander, Australian, etc. etc. Watch how much Maori people identify with Rastafari, why is that, cos they are dispossessed, they deal with naturality and they are warriors. All things which Rasta emphasizes.