The problem is with people who seem to think that there is really anyone who's arguing that a God does not exist, at least in this thread.
I, and no atheist I know will ever claim that God does not exist. The lack of evidence is all I need to say that I do not believe that one does exist. Under MY definition of the word Atheist, it merely means the negative of belief in a god, rather than the positive belief that there is no god. The two are entirely separate ideas and do not share anything between them philosophically. I agree with Jay in that one cannot defend a position of actively believing in the non-existence of something without proof that it doesn't exist, BUT that has never been what Atheists in general have tried to support. There are definitely morons out there on the internets who will spout off without thinking, but this just demonstrates one thing:
There is no central dogma that defines what an Atheist is. It is a label of exclusion, not inclusion. You can only tell what a person does NOT think if they call themselves an Atheist, not what they DO think. The idea that you can twist a person saying that they don't believe in a god into they believe that there is no god is asinine.