Whatever it is, the guilt of rejecting the Judeo/Christian god is there whenever I mention it.
i just look at it like, if you believe in god(s), you're a theist. if you don't, you're an atheist. for me, atheism wasn't a label i aspired to, it was the only one that fit. (i hate labels anyway. people judge the label rather than the person) the more i learn and the more i see, the more convinced i am that there is no proof or evidence that requires god(s) to exist. therefore, i don't believe in him/her/it.
this is one of those things i always laugh about. people tend to shy away from the term 'atheist' in favor of 'agnostic' thinking that it is perhaps a more open-minded version of the atheist. agnostic just means that you don't know what you believe. being an atheist does not mean that you have shut the door, case closed, there is DEFINITELY NO GOD. atheism just means that you don't believe in god. its implication is that should evidence present itself in His favor, an atheist's stance will change. (which is probably the exact reason some label themselves 'agnostic')