When I call myself an atheist, I mean only that I do not believe any God exists. You can't draw any other inferences from just this label. If you want to find out what else I mean, you'll have to actually read what I write. Indeed when anyone calls herself an atheist, that's the only inference you can draw from just the label. You cannot infer that she is a skeptic, a materialist, a naturalist, a liberal; you cannot infer that she is religiously, theologically or philosophically informed or ignorant. You cannot infer that she did or did not come to her atheism by any deep philosophical or intellectual reflection. If you want to find out more about what that person believes, you'll have to ask her.
When atheists insist on the very broad and generic definition of atheist as "one who lacks belief in God" (I would add "and who self-identifies as atheist") they are not saying that this definition is all there is to atheism. They are saying only that this definition is pretty much the only thing that (almost) all atheists have in common.
I self-identify as a communist. And by communist, I mean by that label only that I believe that the United States in particular and humanity in general would be better off socializing the ownership of capital, the means of production. Like my atheism, if you want to know what else I mean by communism, you'll have to ask me.
One thing in particular that irritates me is the inference that by calling myself a communist I must therefore mean that we must replicate the entire political, cultural, economic and historical experience of the Soviet Union, China, Cuba, Vietnam or (god help us) North Korea and Cambodia. All at the same time, including (a la Ned Flanders) all the bits that contradict the other bits.
Look: History is insanely complicated. All sorts of wild shit happens for all sorts of wild reasons, some of them ineluctably mysterious and others mind-bogglingly stupid. Even a lot of the good shit happens for incredibly stupid reasons. And all substantial nations, societies and cultures have so much blood on their hands that appeals to purity are always not just failures but ridiculous failures.
My loyalty is to the present and future, not to the past. My loyalty is to humanity, not the Soviet Union or China, past or present. Yell at me until you're hoarse about the sins of Lenin, Stalin, Mao, Castro, Kim Jong Il, or Pol Pot and you're not going to budge me from my communism. (Similarly, I tend not to emphasize the particular sins of capitalists; I look for structural, systemic failures, not just instances of individuals behaving atrociously.) If Mao did this that or the other that was bad, well, OK, let's not do that. If you want to try to budge me from my communism, you'll have to argue that socializing the ownership of capital is itself bad, or can be implemented only in bad ways, not that it happened to have been attempted in the past in bad ways.
It's not that the Soviet Union, China, etc. are completely irrelevant, either. There's a lot of evidence there, good and bad, and one of my goals in going to college is to actually study the historical evidence in a rigorous way. If you want to make an evidentiary case using the USSR or China, by all means: I'll pay close attention. If, however, you want to scream, "THE USSR WAS TEH SUXXX0R! THE USSR WAS COMMIE! THEREFORE COMMIES ARE TEH SUXX0RS!" I'm going to dismiss you as an irrelevant and irritating fuckwit.