Many religious and spiritualist people say that as if it is some form of defense when they are demonstrated to believe unreasonable and/or unsubstantiated things. It's basically an ad homenim attack to help them feel as if the position contrary to theirs was as illogical as their own.
Do you have any good reason to claim that atheism is a religion anyway? (note my other comment where I explain why it's not)
I haven't heard it, I don't know many religious people, but I guess I can imagine it being used as a defense.
Agnosticism seems to me like a much more scientific approach to the nature of reality. Not being able to prove something doesn't prove the opposite to be true. I think agnosticism allows you to prefer to believe in no deities without ruling it out entirely.
Agnosticism and atheism are not actually on the same spectrum. Agnosticism is about knowledge while atheism is about belief. Being gnostic means that you claim to know where a deity exists. You can lack belief in a deity without claiming to know for certain.
Your positions on gnosticism and theism don't have to be aligned so you can be a gnostic theists, an agnostic theist, a gnostic atheist or an agnostic atheist.
That is obviously correct. But that doesn't really talk about the general atheist position. When you lack belief in a claim, this doesn't mean that you claim the opposite to be true. You just see no good reason to believe the claim.
Let me explain it from my personal point of view as it would be less confusing. I personally don't believe that there is any convincing evidence to believe that any god exists and thus I do identify myself as an atheist. But I don't claim that it is 100% certain that there is no god as you can't really prove a negative. The exact same logic applies to ferries and leprechauns. You could never prove that ferries and leprechauns don't exist with absolute certainty. The only thing you can do is examine the available evidence and conclude that none of it confirms the existence of ferries and leprechauns. But since we have a lot of data and none of it confirms or implies their existence, it's perfectly reasonable for somebody to not believe in ferries or leprechauns and saying that the logical position is really in the middle ground between believing and not believing is actually fallacious.
In the same way, we have gathered piles of evidence on how the universe works and what the universe is and since none of it proves the existence of god, it's perfectly reasonable to not believe the yet unsubstantiated claim that a god exists. Thus it's quite justified to call yourself an atheist in that case. And this is what I have chosen to do. I don't feel like adding the qualifier agnostic in front of the word atheist despite the fact that it certainly applies for two main reasons - on one hand, it offers very little additional clarity and on the other hand, many people unreasonably view it as the middle ground between theism and atheism and I don't want to fuel a misunderstanding of my position by adding it.