I'm pretty sure it was a Pre-Columbian civilization, living either in Colombia or Brazil, conquered and/or enslaved by the Incas. I recall reading that they didn't believe in any form of violence, and preferred being wiped out completely (or enslaved) than to fight back.
It's possible I'm remembering wrong. I've read that enslaving and annihilating conquered civilizations was not the Inca Empire's policy, and I've read about the Moriori genocide, that resembles some of the description I gave. Still, I don't think it's them, and I have a feeling there was a South American civilization that had something similar happen to them.
Thanks.
You might be thinking of the Moriori of the Chatham Islands.
They were a Polynesian people, believed to have been part of the same group as the Maori. This NZ government website has a good overview:
http://www.teara.govt.nz/en/moriori
The Moriori followed Nunuku’s Law, which prevented murder and ritual cannibalism. I have also read and article or two that suggested it could also have been a response to limited resources and creating a sustainable population.
In any event, an encounter with the Ngāti Mutunga and Ngāti Tama Maori showed that pacifism only works is everybody plays by those rules. There was much slaughter and enslavement, but there has been a revival of Moriori culture over time.
Not in the New World, but Cathars.
Pope Innocent III launched the Albigensian Crusade against them and wiped them out.