Maybe it's a false impression, and it's certainly not uniform, but there appear to be some "hot spots" of commonality among atheists. Not that all share them, but that if a person is an atheist, there is a higher chance of them also having certain traits or interests. Knowledge of religion, for example. A vocal atheist (yes, I'm shifting the target) is more likely to be knowledgeable about religion than either a religious person or someone who identifies as unaffiliated. They're more likely to value science and sound reasoning. Perhaps, more likely to identify as liberal than conservative. Maybe this is a false impression, but I would lean toward believing that atheists, as a group, differ significantly from average on one or more traits or whatever. It may just be a side effect of my hanging out with a certain segment of the atheist population, but my hunch is that the similarities among atheists extend beyond just their views on the existence of gods. Maybe I'm off base, but I think Lek has a point. It's just that the commonalities are not well defined, and, not viewed as necessary parts of the definition of atheist.
Or maybe I'm completely off the wall.
Or maybe I'm completely off the wall.