As for the one billion figure, it was actually a conservative estimate on my part, so after hitting google here's a reference for you. "According to University of Hawaii political scientist Rudolph J. Rummel,the total number killed in all of human history is estimated to be about 284,638,000. Of that number, 151,491,000 were killed during the past 100 years. The single largest killer in all of human history is, by far, atheistic Communism with a total of 110,000,000 … over 1/3 of all people ever killed! If we add to that number just two other regimes where religion of any sort was strongly discouraged, Nazi Germany and Nationalist China, the number rises to 141,160,000. Almost 50% of all the killings in human history were committed in the past 100 years by regimes that either actively promoted atheism or strongly discouraged religion."