It's not even a matter of rationality. If their premise was true, all of their conclusions would be
perfectly valid. If the Bible, as written, it truly infallible, then the world really
is 6-10,000 years old.
The problem is that the premise has no evidenciary basis, and a mountain of contradictory evidence (including contradictions within itself!).
They're willing to give total confidence, even above what they see with their own eyes, to the Bible, because they beleive it is the literal Word of God.
Given that premise, everything else, including denying uniformitarianism (except when it suits them) and handwaving the contradictions that look to the rest of us like cognitive dissonance are
completely rational.
The problem is that the only evidence for the existence of the deity is in the book...and the book is only infallible if the deity wrote it. The premise is fallacious, so any conclusions drawn from that premise, regardless of how rational the reasoning, are similarly flawed.
Every time a fundy breaks the laws of thermodynamics, Schroedinger probably kills his cat.
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