Evolutionblog has a great post about Interpreting Genesis. The author, Jason Rosenhouse is responding to an essay by Kenton Sparks, a professor of Biblical Studies at Eastern University. Basically, Sparks argues that the Bible was never intended as a science book and that's where modern creationists err in believing it to be one.
Rosenhouse disagrees and writes [about creationists]:
"Nor do they believe that the early chapters of Genesis were intended primarily to teach us science. In their view the function of these chapters, as with the rest of the Bible, was to give us information relevant to understanding our predicament as sinful human beings.
However, they do believe the Bible is inerrant on any subject it addresses, and if that means accepting what it says during its very rare excursions into science then so be it."
Bingo. Some people believe on can argue with young-earth creationists by discrediting their bad ideas about science. Nope. Some people think we can get around the conflict between science and scriptural literalists by claiming that "Genesis is not a science book" (Kenton Sparks' argument). No again.
To really understand where young-earth creationists are coming from, you have to realize that their entire theology is bound up in a literal interpretation of Genesis because that explains why there's evil in the world, why man needed salvation, etc. That also entails, by necessity, a belief in a young-earth and divine creation, not just of man, but of all life since there was no death before the fall in the Garden of Eden.
Giving up a belief in a 6,000 year-old world is tantamount to giving up a belief in God. Science isn't going to easily win that argument.