Do you think people didn't know it was wrong to kill before moses wrote the ten commandments?There is no atheist church with a mission to convert people to atheism, there is no atheist-outreach program.
Could that be because there is no divine repercussions to wrong doings in atheism? As Christians we believe in a higher power and good commandments. Heaven and Hell and much more. We reach out because we care and do not want to see anyone to live eternally in a place unfathomably horrific. Of course I'm not saying atheist are bad, we just care. I mean it's hard to say this earth and the people in it were put here by chance. Science can't even prove anything and the more they try the most they see there is a divine God.