Words have meaning because they describe difference. If everything was 'red' there would be no word for 'red' as its meaning is derived by being able to say 'not green or yellow or blue...' To simply equate all possible thinking states as beliefs we negate the need for the word however we recognise linguistically that there are states of disbelief. Disbelief is not a subset of belief it is its opposite. Atheism isnt a belief in no gods. It is to be without theism. What I have mentioned before and what some people are straining to prove is that some atheists believe in anti-theism or are opposed to theism. Hitchens wrote one of his books on this. Most atheists I have met believe in humanism in one form or another so if you wish to talk about belief or belief systems that could be a fruitful avenue of discussion rather than trying to argue that my(others) lack of Ganesh statues and a rejection of the literalness Odin is an an example of believing in something.
The motivation to define atheism as a faith based belief (a refinement of belief indicating that it is not supported by observed evidence and for the religious is seen as a virtue and mark of committment) can only, I suppose, come from a recognition that faith is an inherantly unsupportable position and is always at risk from new experience. If positions that are anti-theist OR threatening to faith can be shown to suffer this same fundamental weakness , faith, then presumably they can be dismissed. Ironically fundamentalists often present great examples of critical skepticism but they only ever apply it to threats. They have the skill but not the wisdom to use it fairly.