The notion of conscience seems meaningless without Faith in God. It becomes just a sociological fear of what the neighbors would say if they knew. Those "Xtians" who did Hitlers and Stalins bidding were not Xtians, clearly, when put to the test. By definiton they did not make the grade. Most atheists are theologically naive, what they reject is what only the naive believe, and quite understandably. If only they knew better, then they might find the faith and even perhaps the grace.