Bible is inspired in that it is an accurate record, but there are many things God does not approve of that are recorded in His Word. The moral implications that you and I read into this are not quite here in the historical record. Abram and Sarai were brought up in Ur of the Chaldees where this was a common practice, and the moral angle is not the thing that for them was so wrong. The terrible thing was that they just did not believe God. The wrong that they committed by Abram taking Sarai’s maid