Honestly, it really does come down to final authorities. The creationist position ultimately boils down to this: the Bible is the word of God, and all evidence must be interpreted in light of scripture. In this respect, the origins debate becomes a war of world-views.
But isn't that anti-scientific in the sense that it poisons the well? Going into something with a massive baseless assumption already taken for granted doesn't seem wise.
You're making the assumption that what we define as "science" necessarily must be the final authority when it comes to worldview and historical issues. What you call "baseless" is what a creationist would call faith, which we see as a good thing (and necessary for salvation) rather than something bad. This is the fundamental divide here.
As Evangelicals, we believe that "the beginning of wisdom is fear of the Lord." Would that impact our worldview and understanding of historical and scientific issues? You bet! Is that "poisoning the well"? Well, that depends on your worldview.
For what it's worth, I happen to now know personally chemists, biologists, and physicists who are all ardent young-Earth creationists at my new church (which I've started attending near my college). I'm personally not necessarily completely on board with the YECers (though much moreso now than I was in the past) but I do very much respect the viewpoint.
Science is the most effective and accurate method of investigating phenomena and objects that make up the material world. Religion cannot, and should not compete in this field - just like science has nothing relevant to say about greater metaphysical queries. If both creationists and Dawkinsian atheists could understand that, a lot of epistemologically fruitless bickering would be avoided.
