Ok, let's see if we can make some sense out of the terminology.
There seems to be some confusion about what atheism and agnosticism are.
Atheism is not denying of God's existence, it's denying the existence of divine on a conceptual basis.
This is pretty much what I tried to illustrate with my example about a simulated universe in my earlier post.
For the sake of the conversation, let's assume that a single entity existed before our universe, and created our universe with all the mighty computational powers at their disposal, and our universe is running on their computer system, and that the entity either has or doesn't have direct access to simulation parametres (it doesn't relevantly change the analogy as both points of view exist about God in theism).
Most would argue there would be nothing divine about such a being, yet it would be exactly identical to the concept of God in most monotheistic religions when viewed from the simulated universe. So, what exactly is it that makes a being qualify as a "god" or "divine"? Sufficiently long oral tradition or old enough written text describing the entity and names them as divine god, rather than simply a being with extraordinary (from our point of view) powers?
Atheism takes a point of view that divine does not exist, that division between "divine" and "mundane" is completely arbitrary and needless. In other words, the position of a-theism is that theism (as in, concept of divinity) is fundamentally flawed way to describe the world around us. In atheist's perspective, theism creates a baseless border between different parts of the universe; as the polar opposite of theism, atheism favours a more holistic world view that doesn't automatically create any fundamental difference between sentient beings just based on their power levels or other attributes. We are all the same, gods, humans, aliens, animals, people, beings... wouldn't a God to us be just a regular person among his own people?
In other words, I can't really say for certain that a being described as "God" in judao-christian tradition does not or can not exist. There is, even if rather unlikely in my opinion, the possibility that such a being does exist, and it would be rather unscientific of me to claim with any absolute certainty that it doesn't exist.
But I can say pretty certainly that (in my opinion) there would not be anything divine in it; such a being would be a natural phenomenon just as ourselves, or gravity, or the rest of the universe, or the universe that houses the computer system running our universe as a simulation.
If someone wants to claim there is something divine in something, the burden of proof is on them, just as the task of falsifying the hypothesis falls to those who can do experiments related to it. As an example, it was long thought that flies spawn out of nothingness and that was to some seen as an example of divine life-creating force in action.
Further inspection revealed the microscopic eggs that their larvae hatch from, which put quite a crimp to the divine life-creating force hypothesis, as you may imagine.
TL;DR: Atheism doesn't really bother denying the existence of individual deities. It just says if they exist, they are not divine, and questions whether it is appropriate to pledge servitude to a being arbitrarily named God, when the concept of "divine" loses its meaning.
Some atheists also criticize churches of mismanaging the religions, regardless of the perceived pointlessness of religions in the first place, and urge people to think to themselves rather than submitting blindly to dogmas thrown at them by authority figures (parents at first, later also religious leaders). But, I would view that as more of a socio-political issue than a theological or metaphysical one.
Agnosticism, on the other hand, takes a more of a middle ground position about the existence of divine. What agnosticism says, quite simply, is that we can not gain objective knowledge about the existence of the divine, by the definition of the divine. It is a position that, due to some properties typically associated to divinity, says that since the divine cannot be researched, we can not and shouldn't form and definite statements about its existence one way or another.
Or, as Neutral President would say: "I have no strong feelings one way or the other".
Now, where would I position myself with regards to these definitions? I'd have to say I'm an atheist first and foremost. However, there is one single thing that I could acknowledge as divine, and that is the sum of everything that exists (nested universes or not, this definition includes everything that exists). That is the only thing I could consider "divine", as every other subset of it is smaller than the full set of existence.
Now, if that superset of existence happens to possess a mechanism of being sentient, that sentience I would consider a divine being, and might even dub it "God" if the word had meaning for me.
My position at the moment is that the existence of such superconsciousness is unlikely, but completely denying the possibility of its existence is something I don't want to do either.
As such, you could call me an agnostic, with a provision that the only theism I could find acceptable is pantheism, and even that I find unlikely.
If you have trouble defining what you are, or what someone else is, start with asking how you define the concept of "divine" and whether or not you believe such thing exists. That is much more sensible approach than asking "do you believe in God (which one)?"
