Of course, I couldn't agree with you more. However, you're never going to convince those folks, because you are beginning from a fundamentally different set of presuppositions about knowledge and reason, than the theist. He will never give up the notion that he can 'know' things that are undetectable to the senses, and that syllogistic logic alone is enough to 'prove' that he knows it.
Of course, we see this as utterly irrational, because we argue that the mind can know nothing other than what arises from concept formation derived from sensual data - and that syllogistic reasoning does not trump material reality.
However, the theist will argue that to claim knowledge of the unknowable (in the positive assertion that it does not exist) is irrational precisely because it is unknowable, and therefore, it is the scientist who is making the unfounded assertion. To which, the scientist can easily argue that the theist has undermined his own argument by describing what he claims to be 'non-sensual reality', as unknowable, he has conceded that he does not know either.
At which point, the two are locked in the horns of an agnostic dillema, and so on, and so on, and so on, ad-Plantinga-infinitum....
Not that I'm trying to mock YOU, Niels. I mock the whole process. At some point you just have to throw your hands up and say: I'm not going to waste my life anymore...