Again, only religious people feel the need to categorise atheism as a religion when the only thing that makes someone an atheist is their non-belief of a supreme entity.
There are no defined set of rules that atheists have to live by, nor specific places, people or entities they have to worship, nor things they have to believe for whatever reason, so there are none of the defining elements to make atheism a religion.
If I, an atheist, were to wake up tomorrow and decided that I now believe in the presence of a supreme entity, would that mean I now instantly have to follow a particular set of rules that I have to live my life by? If so, which religion have I instantly become to know what rules I should be following? And if my religion is suddenly dictated by which entity I believe in, what would happen if I believe in more than a single supreme entity?
My point is that you can both believe or not believe in a supreme entity and still not have a religion. It's only narrow mindedness that creates the need to categorise everyone into a religion for reasons that I purely feel are self serving.
There is only one reason why you are an atheist... only one. Because you say it. That's all. Not because you practice atheism. Not because you believe you are an atheist.
Check out #6 of
religion at Dictionary.com -
http://www.dictionary.com/browse/religion?s=t.
Religion fits everybody.

I'm curious BADecker, enlighten me please, how exactly does someone practise atheism?
That's the trick, right? Practicing, right? Since an atheist knows that God might exist, he knows that:
A. He doesn't know that God doesn't exist, and therefore can't believe atheism when he knows the opposite might be true;
B. He doesn't know for sure that God doesn't exist somewhere, he is setting himself up as god over God by proclaiming that God doesn't exist.
All this means is that either the so-called atheist is setting himself up as god, or acknowledging, inwardly, that he isn't an atheist. This makes atheism in the atheist to be non-existent. What the so-called atheist is doing is something else... not atheism. Part of it is lying.
So, how in the world can he be practicing atheism?
