In the Middle Ages before, say, the 12th century, religion was something people did, not something they thought about. The did accept or believe that there was a spirit world inhabited by saints, demons, God and whatnot. Their practices were based on the use of ritual to entice the saints to intervene on their behalf for various needs. The specifics of their belief system did not exist in a detailed theology and would not until the consolidation of royal power at the end of the 12th c.
I should also mention that while Hitchens was a great writer and Dawkins a great scientist, neither of them are historians. Consequently, while their cases against the existence of gods or anything supernatural are pretty compelling, their indictments of religion as purely evil institutions is only partly convincing when one realizes how ecclesiastical and secular norms influenced each other. My point is, we do not have a case were merely not believing in god anymore by a large number of people will do much to cure the world's evil.