Respect his opinion and not join.
The only reason why someone would join such a server is to start some sort of flame war, or argue. You are the one who started it by joining in the first place to post. Usually servers such as "No Christians","No Atheists"."No Blacks","No Jews", and etc; are ran by the worst of each different group (most of the time the opposite of the said group). So don't try to say that this is typical Atheist behavior (which is what I got out of your posts).