ivolt:
When they can't convince their fellow smart citizens.
They spread out to uncivilized and unenlightened part
of the world, where there are sizable population of the
gullible people and desperados.

Jesus said, " Go ye into all the world and preach the gospel to every creature. He that believe and is baptized shall be saved. He that believe not shall be damned (Mark 16:15).

It is not the job of the missionary to change anyone. Their job is to preach. Repentance and faith in Christ is up to the individual.