Someone who does not believe in a god, and always mentioning how Christians and other religious people have murdered many people throughout history (even though atheists have killed millions upon millions of more humans in just the 20th Century alone).
Sarah: Hey Greg, I'm an atheist; do you know how many people were killed in the name of God?
Greg: Well, those people weren't really Christians, because real Christians don't murder. However, do you know how many more millions of people were killed under atheistic rule?
Sarah: Errrrrrrr, um, dunno.