"Atheists have no scientific proof (usually their own criteria) that God does not exist." - Almost true. There is no scientific evidence that anything nonexistent doesn't exist - goes for unicorns, dryads, centaurs, flying spaghetti monsters, and gods. What we do have is statistical evidence that there are no supernatural beings, in that so far, every time anyone has tried to explain something using the supernatural, science has demonstrate that No, it was natural.