Atheism? If there's no god there's no religion is there - can't have it both ways smartypants.
You can be a fanatic
about there not
being a god which can grow to Torquemada proportions (only still not believing in a god(s) naturally).
Personally I find it easier to just take the p*ss rather than have stand up rows about it - but I do tend to reserve that just for Catholics since I know the score there and leave other sects to themselves as they don't really interest me as such. Atheism is about god and the lack of them - that's why it has the 'THE'.
If you believe in evolution or UFOs or whatever then those ain't a god either are they, but it's still belief of a kind though you can get 'religious' about if it approaches religious fervour
but it's still not a god so it ain't religious at all. Just something you're fanatical about. Fanatics of any type tend to be hugely boring I find, but that's just me - I haven't got the energy or will to argue it...