Or say that without religion, the world would be all sweetness and light, not realizing that many of the major wars and conflicts that have gone on in the world have not been because of religion (WWI and WWII, certainly the two greatest of the 20th century, were NOT fought over religion). When you point this out, they hand wave it away, and say it's just people making excuses. "Oh, religious people just like to say, it's only humans that are like that!"
But um, who the hell invented religion in the first place? (Studying history, I'd say nationalism and a desire for territory and conquest was probably a bigger motive than religion.)