In the last century, anti-religious types have killed at least an order of magnitude more innocent people than religious types.
And Christians have killed, for what they believe to be Christian reasons, very nearly zero innocents during this period. Muslims have killed a great many more for what they believe to be Islamic reasons.
Go back a ways in history, and the comparisons get a lot less clear cut. But for the last century or two, the comparison between the three groups is as clear as can be.
I tell them, "Yes, and 500 million years ago, dinosaurs roamed Manhattan, but I don't live in either of those times, so I don't worry about dinosaurs or Christians trying to kill me!"