Atheism is a religion.

[Mister Agenda]

If you don't believe in God, you're ALREADY an atheist,

No. If I dont believe in God that is what makes me an atheist. That is what qualifies me as an atheist. Whatever it is that it took you to through that path (it's either skepticism or curiosity) nevertheless the main reason is your disbelief.

The disbelief is the result of the process you describe, not the reason.

it can't be the reason you became one.

So you are telling me that there are other principles in atheism besides not believing in god?

No, I'm not. And that's not a principle, it's a condition of being, like albinism. I am in the state of not believing any deities of real, which means I'm an atheist. I don't hold it as a principle that there's no God...that would be religiously dogmatic, wouldn't it?

This is like saying someone became a tire salesman because they started selling tires.

Yeas so?
Hey Tom how are you what have you've been doing.
I became a tire salesman.
Really hows that?
You see last month I started selling tires….
I don't find any flaw in that logic.

Tautologies, while true by definition, are devoid of explanatory power. You don't know any more about why Tom became a tire salesman after that 'explanation' than you knew before it. It being logically sound doesn't make it an actual anwer to the question being asked. In effect, 'I started selling tires...' is a non sequitur.