If one claims there is a God, they need to prove there is a God with scientific evidence for it to be considered true. Otherwise there's no reason to believe in him any more than you believe in the flying spaghetti monster. Correct?
Why would the burden of proof fall on the agnostic to disprove the claim that does not have any observable evidence? (books written by men do not count as scientific evidence). In what strange world do we live in where a claim with no evidence (actually having evidence that directly contradicts the claim) is considered true until it can be disproved? You might as well say "The flying spaghetti monster exists until you can disprove his existence, otherwise, you're wrong", which as I'm sure you'll all agree is ridiculous.
Religion has actually tried to adapt to contradictory scientific evidence by changing their standpoint from "this is the unaltered 100% true word of god as it happened" to "ok well maybe the words were more vague and metaphorical and genesis days are actually millions of years" etc. It shows that people are so strongly addicted to spirituality that they won't let go even in the face of mountains of contradictory evidence, instead trying to shape their belief into a more modern and attractive package. Illogical claims are still illogical however, and it all still boils down to the same general point, the claim isn't right until proven wrong.. its wrong until proven right.