I have noticed that according to {Bibolators} one book in particular, Genesis, is considered literally inerrant, yet other books, such as Deuteronomy or Leviticus can just be ignored depending upon the personal whim of the fundie.
i'm going to offer a simple explanation, and one that will sound incredibly insulting at first, but i'm sure that many will admit to.
it's because genesis is the first book of the bible, and
that's all they've actually read. the "it's one book, start at the beginning" mentality comes into play here. if you can make i through numbers, you've got some determination, but leviticus will shatter that. what a boring read those two books are! after that, all your average fundie really knows are the "proof texts."
as dwise1 states, it's all about
fast indoctrination these days, and not actualy open and honest bible study and discussion. so people get all concerned about genesis being literal, without being too aware of books like kings (another boring read). they might know some isaiah here and there, but you'll be hard-pressed to find someone quoting the minor prophets. and they'll pick up on the "hot button" talking points, like homosexuality, without really much having processed even the message of the gospels. why, the very chapter of leviticus between the two "no butt sex" commandments says "love your neighbour as yourself."
...how Biblical fundamentalists pick and choose what portions of the Bible that one should live by and what portions one is allowed to ignore.
this is actually a sort of minor issue, i think. what people choose to follow or not follow is a personal decision, between them and their god. the problem is that they just can't leave it like that for
other people. it seems to me that if we are saved by grace and grace alone, and we are all sinners, we have no right to condemn others for breaking rules we mostly choose not to follow. the fundamental message of the gospel is one of love and compassion, regardless of the law. when christians ignore
this part, and choose to treat others with scorn because they do not follow the law, then it is somewhat fair game to turn their own claims around.
as jesus said, "judge not, lest you be judged." by the standard you condemn others, so will you be condemned. but forgive, and you will be forgiven. it seems to me that if we pick ONE part of the bible and ignore all others, it should be this part.