Allow me to point out one critical difference. A Christian (and probably true for many or even most other religions) believe that there will be a point of judgment, and a salvation from that judgment. By presenting their views as persuasively as possible may lead to the salvation of another. What motive does an atheist have for similar behavior? I submit, nothing similar.
I disagree completely. An atheist's motive is to awaken someone from a delusion so they can actually deal with what IS as opposed to what they wish were so.