Moral values are shaped by societal norms. Society evolves, and its moral values evolves with it.

And for christians that think that christian moral is absolute and set in stone, in the bible, things that we think are very wrong are seen as rightful: incest (all sons of Adam and Eve marry their sisters), slavery (think about Abraham), adultery (also Abraham), genocide (that one happens so many times...), murder for money (the first christians use their new divine powers to murder all the new christians that doesn't give all their money to the nascent new christian community). The list goes on...

Probably we do things that generations to come will find horrible. We just don't know better.