Scientists often believe in unproven conjectures. They have arguments and intuitions and posit theories. These theories are eventually tested. For instance Newton believed that without air resistance any two objects would fall at the same speed. This wasn't tested until well after his death, he had some evidence for it, and some evidence against it, but was able to pick a side without having conclusive evidence. All of theoretical physics is done by reasoned conjectures. The theory of relativity involves objects at speeds we are no where close to producing so can't be experimentally verified for large scales. Yet we still have conjectures, some of which are right and some of which are wrong. Dawkins has even pointed to an example in Biology where the two conjectures were polar opposites, and reasonable scientists held both positions until further evidence ended the debate.

If you present the world with a widespread correct proof that god does not exist you would reduce religions down to a few radical fanatics, determined to deny the truth. In the absence of further evidence however, I contend that both positions are reasonable.