I was watching a debate to do with religion and the "Hitler, Stalin and Mao" subject came up. It's a retort made by religious proponents in response to having the great evils religion has been responsible for pointed out.
"...when you talk about the needless suffering that religion has caused, I think it's time for me to address the historical record; because I think that religion's record is nothing less than exemplary compared to irreligion..."
I could just see it coming as he spoke, it's always mentioned - "religion might be bad but" Hitler, or Stalin, or whoever. When he said it I could hear the usual responses in my head, but they've never satisfied me. Then it seemed to clear up for me - the argument is not that religion simply makes the world worse but that it's in direct opposition to good in a lot of ways. So whether or not it's done good it frequently stands in the way of it and this is gravely important.