Nothing gets the blood pumping like discussing, more like arguing, religion with atheists especially in the anonymity of the Internet. In my experience, I believe there are three kinds of atheists out there. There may be more, but I really think that most atheists fit into one of these three categories. This is not an assault on atheism, but just some general observations.
The first category of atheist is the intellectual atheist. This includes people like Richard Dawkins, Christopher Hitchens, and other members of the "new atheism." These people see and judge everything in life solely on the basis of logic and empirical evidence and if you cannot offer proof they want nothing to do with you. In fact, they will call you an intellectual weakling and kick copies of Stephen Hawking's work in your face. These are the people who truly believe there cannot be anything higher or greater than their own intellect and so God cannot exist. These include many college professors and scientists.
Second are the hedonistic atheists. These are the folks who live by the mantra of "if it feels good, do it." They do not want to believe in a higher power or the ethics that belief entails. They see that this life is the only one we have and so let us eat, drink, and be merry for tomorrow we die. A dangerous question surrounding these atheists is whether or not the lack of a theistic ethic affects their decision making? If there is no belief of God holding them accountable in the after-life, what prevents them from engaging in dangerous behavior, aside from legal ramifications?
The final category of atheist is what I call the wounded atheist. These people were so hurt, physically, mentally, or spiritually, by the church or by someone representing God that they reject the idea of God altogether. I have seen those abused by priests, pastors, and church members turn away from the faith because of the pain cause by people of God. I have seen the Church turn its back on people because of past sins. In any case, this kind of atheism is the fault of the Church. We as the Church must be cautious and careful with God's children because when atheism is cause by our carelessness we are guilty of the greater evil.
I do not present these categories as condemnations. But simply as my own observations and experiences. Of the three categories I believe that only the third can be brought back into the faith, but it would take years of counseling, a great move on the Church's part, and the forgiving power of God's love.