Here is an astonishing, and astonishingly frank and honest confession from a confirmed atheist offering unqualified support for Christian mission. I urge you to read the whole article at Times Online.
"Now a confirmed atheist, I've become convinced of the enormous contribution that Christian evangelism makes in Africa: sharply distinct from the work of secular NGOs, government projects and international aid efforts. These alone will not do. Education and training alone will not do. In Africa Christianity changes people's hearts. It brings a spiritual transformation. The rebirth is real. The change is good.
I used to avoid this truth by applauding - as you can - the practical work of mission churches in Africa. It's a pity, I would say, that salvation is part of the package, but Christians black and white, working in Africa, do heal the sick, do teach people to read and write; and only the severest kind of secularist could see a mission hospital or school and say the world would be better without it. I would allow that if faith was needed to motivate missionaries to help, then, fine: but what counted was the help, not the faith.
But this doesn't fit the facts. Faith does more than support the missionary; it is also transferred to his flock. This is the effect that matters so immensely, and which I cannot help observing."