I think the question had more to do with things like the following:
  • Deuteronomy 25:11 - If two men, a man and his countryman, are struggling together, and the wife of one comes near to deliver her husband from the hand of the one striking him... and puts out her hands and seizes his genitals, then you shall cut off her hand. You shall not show pity.
  • Genesis - The daughters of a God-fearing man, who is spared in the destruction of Sodom and Gomorrah, take him up to a cave, get him drunk, and commit incest with him.
  • Onan - The person who "spilt his seed upon the ground." No, he wasn't masturbating, as the Catechism would seem to imply. He was having sex with the wife of his dead brother - as required by societal law. The idea is that you have to screw your sister-in-law if that brother dies, and that the children resulting will be considered your brother's children. Well, Onan didn't want to give his dead brother children, so he pulled out at the last second and nutted on the ground. (Pardon my vernacular. I think it's justified in this context.) This sister-in-law was then supposed to publicly humiliate him, as was the custom, by slapping him across the face with a shoe in the town square. She didn't get the chance. God saw he was too greedy to give his brother children, and struck him down.
  • Leviticus 11:10 - And all that have not fins and scales in the seas, and in the rivers... they shall be an abomination unto you. (I agree with this, but there are a lot of people who don't, and happily consume shrimp and molluscs, all the while living as devout followers of the Bible.)
These customs would probably be considered wierd by modern standards, as would other biblical stories - for example, I don't think any of us would be interested in selling our children into slavery to "neighboring tribes." I believe that THOSE are probably the "things you disagree with" mentioned in the question.

Or maybe it's the idea that Terra was created in six days.