The basic scientific argument against the existence of God is that there is absolutely no observational evidence for the existence of a God, nor any reason to hypothesise such an entity in order to explain anything that is observable. A very straightforward application of Occam's principle then suffices. Of course this is not a *proof*, but it is a sound *scientific* argument. Proofs are irrelevant here. There is no proof that the flying spaghetti monster does not exist, but that does not shake the faith of the true Pastafarian.
Pat