Agnosticism is the mature stance, because agnostics understand the futility of these discussions and know that metaphysical claims of a God can neither be proven nor disproven.
Logical Positivism is where it's at, when someone says God to me, as an agnostic it doesn't mean anything. To an atheist it would be something which does not exist, but to me, it simply is a meaningless statement which is neither verifiable or unverifiable, thus any conversation of a "God" doesn't hold meaning.
Most atheists I know are atheists because their parents made them go to church or they disagree with some politician telling them they shouldn't be playing violent video games. Some atheists even do stupid things like placing emphasis on things such as Satanism and whatever rebellious shit they can pull just to turn heads.
I know not all atheists are like that, and some even have ethics and morals, but the one's I've encountered where I live are smarmy people who don't believe they should behave as "the sheeple" behave, and thus have no morals or ethics because they believe all morals and ethics are fundamentally linked to theology.