It's true, as the popular atheist meme (*ahem*) says, that being an atheist means only that you don't believe in God, and nothing else. But it's obvious that very many atheists don't really believe that. Otherwise, the very popular sarcastic expression "yr atheistin wrong" wouldn't exist. If a lot of atheists didn't have a lot of other rules for atheistin, that popular sarcastic phrase wouldn't be funny. It wouldn't mean anything at all.
I can't tell you how many times some atheist or another has immediately assumed that I believed God exists as soon as I disagreed with him or her when he or she said that ending religion would end all of humanity's problems, or that Constantine and the Pope wrote the Bible at Nicea in AD 400, or that being an atheist means one is more intelligent than a believer, or that we are all born atheists, or that religion was invented in order to control the masses (In point of fact, there were no masses when religion began: there were no towns or cities, and humans didn't live in herds, but in small bands.), or that religion poisons everything, or -- if you've hung out in atheist groups for a while, you can add to the list yourself. Yes, being an atheist means not believing in God, it means only that, but that doesn't stop some atheists from adding a whole lot of other rules. A whole lot of other things in which you'd better believe. Or else.
It may often seem as if I argue with other atheists just because I am cantankerous, because something's wrong with me -- and no doubt, there's something to that. Don't worry, I'm in therapy, I'm working on me. But there's more involved here, when I or some other atheist keeps saying to groups of atheists: No, I don't agree. (Not always 100% as politely as that. I'm working on it.) We're also speaking up for others who may be more timid. Clearly, for some people, becoming atheists did not mean ceasing to live by a long list of rules, maxims and Truths which for them are not up for discussion. Others of us, however, cast aside the revealed truths of religion, and DON'T want to replace that religious dogma with atheist dogma. We stopped letting clergypeople and holy books tell us what to believe, and we DON'T want atheist leaders and books by Dawkins, Harris, etc, to tell us what's what. We actually want to think for ourselves. (It's not for everybody. Clearly, it's not for all atheists, not by a million miles.)
And wouldn't it be a shame if some timid atheist was scared away from a group, or stayed in a group but was afraid ever to speak freely, because everyone in the group seemed to believe in a bunch of slogans and historical inaccuracies, because no-one ever spoke up against them. Yes, it would be -- no, it is a shame. There are many such groups. If I argue with somebody about whether or not babies are atheists, to a point, it's about semantics. But there's more to it than that. It's also about not just giving up and keeping quiet when others want to force me to conform and agree.
Are you seeing a lot of parallels between the pressure to conform I'm describing in atheist groups, and the squelching of discussion in conservative religious groups? You are, if you're paying attention. Notice I'm comparing these atheist tendencies, not to all religious groups, but to conservative, reactionary religious groups. That's right: in some cases, you're more likely to find an actual discussion about things among believers than among atheists.
Obviously, not all atheists are that fucked up. Obviously, I'm not the only one denouncing atheist conformity. But -- yeah, there could be more of us. More of you could be speaking up along these lines. No pressure. Only the future of humanity is at stake. (Ha, ha, kidding. Sort of.)
Ich wohne in meinem eigenen Haus,
Hab Niemandem nie nichts nachgemacht
Und - lachte noch jeden Meister aus,
Der nicht sich selber ausgelacht. (I live in my own house, I've never copied anyone, and I've laughed at every master who never laughed at himself.) -- Nietzsche