I think atheism being called a belief system when there is no spirituality and religious devotion is fine. It'd be just as fine to compare it to philosophy when it excludes complete religious belief. Calling atheism a dogma is a good middle ground.
I think about my place in the world. I think about morals. I think about my relations to others. I think about how we got here. I think about why we are here. Is that existential?
I'm an atheist who has spirituality, but not in a religious manner. I define spirituality as a feeling that comes about as the result of brain chemistry and environment. And I do not fear death because I feel it will bring peace, which I define as a lack of pain, excitement, happiness- an euphenism for complete nothingness.
My dogma does in itself does not bring me misery. I'm unhappy because of life and mental illness. See, there are more variables to life than dogma. An environment can make an atheist unhappy, due to a lack of acceptance and attacks on their dogma.
Why do some atheist attack religion and religious people? For the same reasons some religious people attack atheist. It definitly isn't a one way street. I've personally had to deal with attacks on my belief. I've also seem people denied rights due to their conflict with the majority of believers (homosexuals for example). This is despite a seperation of church from state.
I don't attack religious ones and systems too much. I have religious friends and family. I need to speak my mind though.