I've heard it asserted that atheism is a claim to knowledge and agnosticism is a claim to belief. A claim to knowledge requires an explorable deductive basis for that knowledge. as in...I'd say just say you're atheists and you don't believe God exists, which is presumably the position you hold. If you lack belief X, doesn't that entail belief Y? E.g. I lack the belief that it's raining outside, therefore, I have the belief that it's not raining outside.
Whether you have or lack a belief is kind of irrelevant and boring in a discussion. From my experience hearing people on this question, it comes down to trying to escape a burden of proof in an argument *shrugs*.
I know there is no Christian God because there is positive evidence against the biblical proposition because x.y. and z make the biblical proposition impossible to me.
as opposed to an explorable inductive basis as in..
I don't believe there is a Christian God because x, y, and z seems to not describe Him. Maybe the Christians are just wrong are there are other possibilities for His character that might make sense if I can explore those.