You forgot to mention Western missionaries. I did my dissertation on this very topic during my masters in social anthropology.
Sadly it is often the case that the bearers of prosletyzation are the first regular western contacts for many remote tribes, engaging in a systematic cultural/cosmological deconstruction and cultural assymilation.
The old excuse of planned assymilation/healthcare/education to justify some of it doesn't convince me it's right. Who are we to impose our will/beliefs/cultural values on anyone else? Grrrrrrrrrrr rant over!
Arrrgghh There be a lot o' long words there - we're nowt but humble pirates! I went to scumbag college - UP SCUMBAG!