"Agnostic," as used here and as criticized by Adams, is most often a weasel word used by atheists who believe atheism necessarily requires a god-hating, Hitchens-esque attitude towards religion and do not identify with that, or who are afraid to admit to their atheism for social reasons, or out of fear that they are wrong and god will punish them (and that calling themselves "agnostics" instead of "atheists" will somehow prevent god from punishing them, the absurdity of which is Adam's point, obviously.

Interestingly, this is not the original meaning of agnostic. A "gnostic" believes that the question "Is there a god?" is discoverable or knowable. An "agnostic" believes that it is unknowable or undiscoverable. Thus, an agnostic atheist is one who does not believe there is a god and believes we can never (fundamentally, not just practically) know if there is one or not. The person you would describe is just an atheist, and probably a gnostic one.

I think the vast majority of the atheists in this community believe they could be wrong, they just assign a very, very low probability to it, particularly with respect to certain specifications of god.