At the risk of going off thread, and with all due respect, the English clergy were up to the slavery traffic to their eyeballs. Others did preach and campaign against it. The abolitionists in the US were regarded as dangerous cranks, and talked of secession.
I can appreciate the great works of the past without necessarily accepting their "moral justice" -- certainly not in its entirety. One of Tolstoy's greatest works describes the really bad things that can happen to a woman who leaves a barren marriage for love. It doesn't end well for her, and while Tolstoy does not lack compassion his book is basically about why she was wrong. I am glad that women taken in adultery these days don't have to cope with such moral justice, they already likely have enough complications to deal with.