When I was in college I got my major in cultural anthropology. One of my classes studies these people, the Yanomami. And let me assure you, the typical anthropological attitude towards missionaries is one of extreme antipathy. (There's your college degree at work!)
One book I've kept over the years was written by Napoleon A Changnon called "Yanomamo: The Fierce People". He had particular issue with the missionaries getting in a huff about "chewing tobacco . . .taking extra wives, or most annoyingly, insufflating their hallucinogens and chanting to their hekura spirits." (pg.206)
Do you know what it means "insufflating their hallucinogens"? They take a long hollow pole, one guy, with all his might, blows the hallucinogens into the nostril of the other. Yeah, fun stuff. Changnon wrote of his experience insufflating some hallucinogens and he says "I called out to Ferefereriwa and Periboriwa, hot and meat hungry hekura, and asked them to come into my chest and dwell within me."(pg.208)
Changnon concedes that a few of the missionaries "were downright humane-given their ultimate goal of destroying Yanomamo religion." --yeah, that enslavement to darkness . . .
Years later, this book came out "Spirit of the Rainforest: A Yanomamo Shaman's Story" by Mark Andrew Ritchie. Mark wrote down the story dictated to him by "Jungleman" a powerful shamen that converted, and - wouldn't you know - be of the people that Changnon worked with. How interesting to read Jungleman's side of the story.
One thing that I found interesting in both this book and in the book "Growing up Yanomamo" by Michael Dawson is that whenever worship and praise was played/sung all the hekura fled, wouldn't come near, and it was a particular peeve of the shamens.
So - today, I'm going to have praise and worship going just in case there are any hekura hanging about . . . .