Having once been an adherent myself, this is my understanding of why Christian Fundamentalists are so zealous about Creationism:
… accept the theory of Evolution as the most reasonable explanation for the variety of life on Earth
….accept the geological evidence that says that the Earth is billions of years old
…accept the astronomical evidence that the Universe is much older than even the Earth
…obviously do not read the Bible literally
…do not believe that the Biblical creation account is true
…cannot trust that anything else in the Bible is true
…cannot accept God’s Word as true
…under the influence of Satan
So, in fundamentalist eyes, conventional scientific inquiry is not necessarily flawed but profoundly dangerous. In order to protect the philosophically unassailable conclusions of Creationism, which are based solely upon Biblical texts, any tactic that can discredit the conventional scientific wisdom is acceptable, particularly the ad hominem argument
But the defense of Creationism becomes more difficult as scientific research continues to reveal evidence for the natural history of our planet and the workings of the Universe. This evidence cannot be ignored so it must be re-interpreted, but always through the lens of the Bible. In this way the geologic and fossil evidence can be explained ‘scientifically’ through the extrapolation of Biblical stories, particularly the story of the Flood.
As it turns out, the Flood is a convenient refutation of just about all the physical evidence that supports evolution and an old Earth, at least for those who believe in Biblical Creation. It is the point at which the Creationists and the Evolutionist continue to bump heads. Because, though the Evolutionists can say that the Flood is merely a convenient myth that neatly gives religious answers to questions about the Earth, the Creationists can reply that yes, indeed it does. The Flood explains everything. But it is no myth
Without the Flood and the story of Noah and his Ark, there would be little if any support for the theory of Creationism. This is the mechanism that provides an air of ‘scientific’ legitimacy to their position, one that incorporates physical evidence coupled with a theory that is irrefutable, as it cannot be tested. When this theory is questioned on the basis of obvious evidence to the contrary, the Creationists are left with no choice but to fall back upon a supernatural explanation that is often the result of a non-contextual rendering of a Bible verse. ( i.e. “all things are possible with God”)
It obviously boils down to a question of faith, not science. If one definition of faith is that it is a belief that does not rest on logical proof or material evidence, then Creationism cannot be called science. Yet another definition of faith is trust, confidence in someone or something, without the necessary evidence to support it.
If ultimately the Creationist position is supported by an article of faith that cannot be tested, then why spend all this energy on modifying school science texts so that they teach Intelligent Design or the ongoing construction of numerous Creation museums (one intent of which is to ridicule modern science and scientists)? It is a classic example of “preaching to the choir” and comes across as a desperate attempt to present evidence necessary to “prove” the existence of God. Because there just isn’t enough faith.