My church did "missions" to Ecuador (read: sending unskilled teenagers to build schools and churches of dubious structural integrity) and there was a big argument one year because the town they were going to was either populated by or near the tribe that movie is based on. I remember a couple of adults talking about "the last time we sent missionaries, they killed and ate them."

It's kind of a trip reading about the actual guys behind the story though. The evangelical culture of the era was so different. While the missionaries were there to convert the natives, they were also there to spread Christian pacifism. There's even journals from Jim Eliott talking about how disgusting he found America's tendency to go to war.