Atheist as synonym for evil (idea)

Actually, this didn't start with Christians, but with pagans, or at least the Greek and Roman pagans, who had just as dim a view of atheists as fundamentalist Christians. The considered religion to be the foundation of society and morality (like fundamentalist Christians), so they considered atheists to be, at best, people without any moral compunctions. In fact, when attacking early Christians, many pagans accused them of being atheists because they denied the reality of the pagan gods.