Coming to the topic of challenging atheists, I am afraid I have to side my fellow brother, Kinanna. I did this quite relunctantly but I want to be honest to say that the word challenge might be 'too strong' a word. Rather, Christians should defend our faith and we are told very clearly that we need to give an answers to people who question us of our faith, especially, the redemptive work of Jesus.
The intend is to ensure that we follow what the Bible and what Jesus told us to do. But instead, I have received tons of emails...literally tons of them from atheists, using vulgar words to 'challenge' my belief. That was not my intention to 'challenge' anyone.
My conclusion, sadly, after all these is that, we have to be prepared to 'challenge' our beliefs, and although I did mention this word might be too strong and my perferred word is to 'defend' our faith, that was not what atheists preferred. We are left, quite unfortunately, wiith no choice but to challenge them.