Actually, there is, though you're right in that it isn't an ideology, because it's the absence fo a belief. There are words to describe abcences, such as asymmetry, apolitical and amoral (not to be confused with immoral, though many do fall into that confusion).
All your examples actually name things that have a particular qaulity described by means of something that is absent: there are actual things without symmetry, there are concepts that have no political aspect, and there are acts that have no moral consequence (or concepts that have no moral aspect). There is nothing that atheism is a name, aspect, or quality of.
It is an attempt to identify a person in terms of what is not true of them. It is like trying to identify a person's nationality by naming all the nationalities they are not. If a person is Chinese, we do not say, that are non-French, non-Spanish, non-Italian, non-Japanese, etc. ad infinitum.
Why would we try to identify a person by all the superstitions they don't hold, as he's an aZeusist, aSwedenborganist, aZoroastrianist, aTheist, a-Allahist, etc. etc. ad infinitum.
If we are not going to name them all, why is one any more significant than any other?
Hank