I think it can all come down to this, simply:
Atheism is based on the lack of proof that God exists. But they cannot prove that he does not exist. Either is possible therefore Agnosticism is the only safe belief.
proving negatives is far more difficult than proving positives
Understood, but neither side backs their point up with any proof.
evangelicals think they do. basically, it boils down to "it is extremely unlikely that all of these things are coincidental." or, "I heard voices!" the latter more frightening.