How it works is that Christianity is exclusive religion by it's nature, and with the world being "why can't we all get along together" it creates conflicts with those who don't like that. Someeople hate "I am the way, the truth, and the life: no man cometh unto the Father, but by me". OK, that being the case, and that it was mandated by
the Great Commission to go out to places like these, they go. It's THE imperative, so yes by what they have learned conversion is necessary. What's not being understood by some here is speaking words as if an incantation isn't going to do anything. When Paul went out, he spent time talking to the people and getting to know them and preaching to them over time. Missionaries spend entire lifetimes doing just that and helping in the community not just as people in a pulpit but health care workers and educators. They become part of the community in that sense. Those they associate with have a choice to accept Christianity or not. It's their choice. Christianity is exclusive in the sense that Christians believe that the way to heaven is through Christ, but you cannot force conversions, because that's a personal choice. You say yes or no. The vast majority of missionaries understand that. A bit of background for context.
In this case, this fellow felt differently. He chose a path that was at odds with his families core values. That you disagree with them is unimportant. To the family it was, and that's why it happened. He understands and it's sad, but life sucks sometimes. He and they went along roads which can never meet.