[ChrisV]

The point is repeatability and falsifiability. If someone doesn't believe that the probability of flipping a coin is 1 in 2, I can instruct them on how to test it to any accuracy they like (it involves flipping a crapload of coins). No theist can tell me how to reproduce their personal religious experiences. The argument of atheists is not that people shouldn't believe ridiculous things (although we certainly reserve the right to make fun of them) but that nobody should impinge on the lives of others based on beliefs they are unable to substantiate to others.