> There's a real problem (in my opinion) with weird evangelical Christian missionaries who treat the population of PNG as some sort of religious terra nullus

The contemporary role of missionaries is complicated. My mother is a (now retired) doctor, who formerly (>10 years ago) worked for a Seventh Day Adventist church mission in the Solomon Islands (I also mentioned in another comment she worked in the PNG, that was with Australian Doctors International, a secular charity–although even part of that work involved working with a French doctor who happened to be a Catholic nun). My mother isn't a Seventh Day Adventist, she isn't even particularly religious (lapsed Catholic) – her personal motivations weren't about religion, it was about charity, and also the professional and personal experience. She just somehow (I think through some work colleagues who happened to be Seventh Day Adventists) became aware of the mission and ended up working for it–it was essentially volunteering, they may have reimbursed some of her expenses, but whatever she was paid was a fraction of what she'd get working as a doctor in Australia. The mission wasn't currently converting the local population – that had already happened generations ago - and much of the local population combined Christianity with elements of their indigenous belief systems. I guess coming from a Catholic background gave her some personal tolerance for the religious aspect, even if it was never her motivation.