It depends on what your classification of an atheist is. For many religious people they see it as rejecting any of the current day religious myths. Strictly adhering to the word, it's the viewpoint that there is no intelligence behind the observable universe.
The former is rational and supported by a ton of evidence, the latter is not. It's possible there was an intelligence that created the universe our planet is in, but there is no evidence supporting that, it's just a possibility. There is no possibility Christianity, Judaism, Islam, Thor, Zeus, Ra or any of the other deities posited over the time of human civilization are real. These have all been debunked and amount to folklore.
Choosing to believe one of the myths is a choice to ignore the evidence because the myths provide something more valuable to the individual than accepting the reality does.
As long as the religious strictly apply their beliefs to themselves and on no one else, I could care less what people believe. We all lie to ourselves about one thing or another anyways.
Can you link me the Christianity, Judaism, or Islam debunking? I'd like to see those.