> If you aren’t sure then why should you say “there is no god”?

I usually don’t say that, although I might, to piss off the fence-sitters ;)

> From my perspective and understanding of the definitions if you aren’t sure, then you are agnostic, not atheist.

One can be both. The point is, “there is no god” involves no more faith than “9/11 was not done by aliens”, so your logic in comparing atheists (by your def) and theists is poor. It is semantically possible to say “there is no god” and have no religious faith.