I don't have a problem with this from a 1A point of view. Let them have their say. It is rude and meant to provoke Christians, but what's new about that?
Recent research places the difference at a critical 30 milliseconds ~ and when it comes to detecting otion that's enough to make you accident prone and unable to think more than a couple of steps ahead.
Frankly, I don't think the Atheists would care to have a scientifically accurate and provable sign concerning their "slowness" posted anywhere.