In fact, the average atheist is a law-abiding, tax-paying citizen; often they are people who you might think of as good Christians. Cardinal Murphy O'Connor, outgoing Anglican archbishop of Westminster Cathedral in the United Kingdom, stated that the lack of faith was the "greatest of evils." As an atheist, I do not think my "sin" is on the level of a murderer or rapist.
If a God exists, which I do not believe is so, I do not believe that such a being that gave me a mind and reasoning skills would be angry at my reaching a conclusion based on those abilities, even if I am wrong. My non-belief harms no one. Non-belief does not lead to great social problems.
This is not to say that many people aren't helped by Christianity, but the idea that non-belief and atheists pose harm to society, in the opinion of the good cleric along with others, is simply a myth. What is in fact dangerous to society is those who show no empathy to others or are driven by a rigid ideology, be it secular or religious.