The problem is that they claim their book is the word of their god. If they can discard parts as allegory, but others as truth, then how do they decide? At whom's whim does the decision rest?
That people need to create new explanations for why the Bible says something that they decided it doesn't mean to say anymore makes me think that the book wasn't right in the first place and people are desperate to keep it relevant. If 'god' didn't want people to think the world was 6,000 years old, why say it was in the book? Seems like 'a long long time ago' would have conveyed the same idea, but prevented people that believe the book to be true from running around with obviously flawed information. Even George Lucas figured out it was easier to be vague, one would think the creator of all things would at least be at that level. That some are 'quite comfortable' with their ever changing assumptions regarding the content of their book doesn't make them enlightened, it makes them look like they would rather change the entire meaning of the book rather than admit it might not be true.
Making one's faith fit science seems to be a lesser evil that forcing the science to the faith, but in the end you are still forcing something to be 'true' when an entirely different conclusion could reached by throwing away the requirement that the answer hold to a bronze age religion.