I think that most new "converts" to an idea start out being very focused on winning >arguments, which probably correlates to grouchiness or at least excuse-making and the >inability to get things done.

I don't know if this is the reason why my 'atheist' friends seem unhappy to me. I think a lot of them are atheist by default, because they haven't thought about the question in years, and unhappy or negative by default, because they don't question that either. It's very easy to be atheist-by-default in my community. Being obviously religious is the thing that stands out.