How was the interpretation of Christianity use to justify slavery?

During the period of American slavery, how did slaveholders manage to balance their religious beliefs with the cruel facts of the “peculiar institution“? As shown by the following passages — adapted from Noel Rae’s new book The Great Stain, which uses firsthand accounts to tell the story of slavery in America — for some of them that rationalization was right there in the Bible.

Out of the more than three quarters of a million words in the Bible, Christian slaveholders—and, if asked, most slaveholders would have defined themselves as Christian—had two favorites texts, one from the beginning of the Old Testament and the other from the end of the New Testament. In the words of the King James Bible, which was the version then current, these were, first, Genesis IX, 18–27:

Explanation:

on my last question

the main objectives of the progressive movement were eliminating problems caused by industrialization, urbanization, immigration, and political corruption.