I'll take your point for the sake of argument.
Lacking a God belief is another belief, that may be true.
But don't take that lack of God belief to equal an assertion that there is, for sure, no God.
There IS a distinction there. That's not just an atheist slogan. The thing is that as an atheist, I think it's perfectly possible that there's a god up there, for which I do not currently have any evidence. Believe me when I say that: he could well be up there right now.. I think it's always possible... but I just think he has never given any evidence that I can believe in, as a grown man who requires facts in order to jump on board his worship train.
I certainly do have a form of non-agnostic "belief": that the reason why most people believe in god today, "religious revelations" (Abraham, Mohommad, etc), are as hokum as any other hearsay people pass on to each other without proof: UFOs, big foot, homeopathy, conspiracies, etc. I do have a belief that those revelations are probably bunk, or if they have truth, then the reason why people believe in the traditions are indoctrinations by society. Almost no one weighs the evidence to arrive where they do. They begin their lives mired in these assumptions. Call me bloody skeptical on these events.
But I'm not closed on that point either... as soon as some theist can give me better proof of those religious events... I'm in.
So yes, atheism might be "a belief" in itself... but it's not a denial of the god possibility as commonly understood. It's a denial of religous hearsay. That's my affirmative belief. People don't have nearly enough evidence to worship as they do, or even assume a weak "ennnh maybe" stance.
If there was good evidence... someone could show me! Hasn't happened in my life.
I'm pretty sure all the theists I've ever met don't have that proof either.