An anonymous commenter brings up some issues that I want to address, perhaps obliquely, by a discourse on Dictionary Atheism.
Dictionary atheism has its uses: for one, it establishes atheism in the most broadest sense as a diverse group about whom it is difficult to draw generalizations. Thus, if you want to criticize specific atheist ideas, it's probably better to criticize the ideas directly, rather than using specific ideas to draw generalizations about "atheists."
I'm not going to address Myers' conceptions of Dictionary Atheism, but I will offer my own thoughts. As noted above, the idea that "atheism," in its broadest, most general sense, i.e. "Dictionary Atheism," has some merit. On the other hand, for many, perhaps most, atheists, myself included, atheism doesn't just float isolated in our minds; it really is part of a larger mental system. I believe that both individually and in general, atheists — especially skeptical atheists — are substantively different from religious people in systematic and characteristic ways that go far beyond the presence or absence of a single belief. As I said, generalizations are difficult to draw from such a diverse group, and all generalizations have exceptions, but this generalization does seem to have good evidentiary support.
I really don't have much evidence, other than my recollection of reading Myers' original article, of the actual position of so-called Dictionary Atheists; it's not a topic I'm particularly interested in. But I suspect that one difference is that Dictionary Atheists might imply that one cannot, by definition, draw any generalizations about atheists; any difference between atheists and theists cannot be associated specifically with atheism. How can one draw any conclusions at all just from the absence of one particular belief, especially when there are so many possible causes (or lack of causes) for that absence?
To a certain extent, that position has merit, especially as a counterargument to some of the stupider claims by theists: atheism entails materialism, reductionism, egotism, asociality, hedonism, etc., ad nauseam.
However, the contrary idea, that atheism is often systematically "hooked into" a broader conceptual framework, also has merit; the idea that atheism cannot possibly be systematically associated with any conceptual framework seems specious. And we see a lot of evidence that atheism really is systematically associated with skepticism, humanism, liberalism (in the modern, American, sense); the extension to feminism, gay rights, anti-racism, etc. seems to follow naturally, at least for a lot of atheists. I would not make the argument that these extensions follow directly from atheism, I would argue that for skeptical, humanistic atheists, these extensions follow directly from the same underlying source as one's atheism. It is inconsistent, I would argue, to say that one has good reasons for being an atheist, but not to apply those same reasons to issues that have nothing fundamental to do with the presence or absence of any gods.
Of course, there are exceptions. Some atheists, perhaps many, do not believe any god exists simply because they have accidentally not been exposed to the various conditions and circumstances that tend to inculcate religious belief. I do think that the idea of god is "artificial," it does not occur "naturally" in the same sense that belief in, for example, objective, external reality naturally occurs. And then there are atheists with a moral, ethical, and political foundation profoundly different from my own foundation of humanism and moral and political equality. I do not believe that anyone needs any particular moral foundation to realize the evidence abjectly fails to establish the existence of any supernatural deity or to understand the vacuity of conceptions of supernaturalism that are immune to empirical inquiry. Even a complete sociopath can be a legitimate, philosophically aware atheist.
But there's no fundamental problem with different underlying moral foundations among atheists. On the one hand, yes, broadly defined, everyone who lacks a belief in god, for whatever reason or no reason at all, really is an atheist. On the other hand, differing moral foundations acts as one of the most important bases for forming distinct interest groups. I can say to Libertarian or anti-feminist atheists, for example, that yes, they are legitimately atheists, but their fundamental philosophical basis for why they're atheists differs substantively from my own. Furthermore, I find their own underlying moral framework to be reprehensible, contemptible, and unworthy of close association.
I intentionally and consciously hold this explicitly divisive position. Moral divisiveness is a fact; to demand that we suppress our moral divisions would be just as delusional, just as dogmatic, as the worst of religious belief that atheists typically criticize.