We're all just angry at god. My all-time favorite. No need to explain to this crowd why that's completely impossible and ridiculous. It's obviously rooted in the assumption that deep down inside, we really do believe, but we're just kind of honked off that he isn't doing a better job at running the universe.
Nope, not even a little.
By the same token, I'm no longer pissed at Santa Claus, even though I told him quite clearly while I was sitting in his lap that I WANTED A RED BIKE, not a blue one.
Somewhat long post, sorry. My first TA post...
Some people think atheist are just posing as such because it's cool, or anti-establishment, or rogue, or some other form of "Oh, he's says he's an atheist, but you know he really believes." A friend said to me once "So.. you...really don't...believe in...god? But you know so much about the Bible." All I could say was, "You've known me for over 10 years, did you think I was pretending?" She simply couldn't fathom a world without a god, or that a friend could truly hold that position.
This exchange happened in front of several of our friends, some believers. The next 2 hours (this was all over beers and Scotches and whatnot) evolved into all manner of religious discussions among a diverse group including a Muslim, 2 atheists, 2 protestants, 2 Unitarians, a Catholic and an apathetic who got bored and eventually played Golden Tee. In the end, my friend was crying, having finally realized the wide range of our friends' beliefs. At that point even the protestants were saying things like, "Of course the bible is allegory! How many animals can you fit on a boat?"
She was crying because she finally, albeit alcoholically lubricated, came to realize that her entire adult belief system was a construct of cobbled-together children's stories. A few weeks later she thanked me and many of the others for helping her see that she needed to look at her beliefs with adult eyes. She's still a believer, but she doesn't assume that everybody has the same religious beliefs that she was raised with in Western Kansas in the early '60s.
So, to answer the original "Misconception About Atheism" question: Most atheists DO know about the alternatives, and most atheists have thought quite a bit about what they believe and consciously decided to be a non-believer for non-trivial reasons.