This always seems to come up in discussions with Christians: What motivation do you have to be ethical if you're an atheist? They never seem to realise that having a god telling you what to do doesn't make you moral, especially not with that terrible Bible.
I got a nuanced response from this Christian -- then his brain stopped. What a shame.
Slaves should be obedient to their masters.
Rape a girl, pay her father, and she's your wife!
God used to like killing gay people.