Kitty_Joanne:
Blasphemy!
Hey! How did you find out my real name?
Everything that has been said to support the idea that consenting-adult incest is immoral (majority opinion, illegality, family/neighbors would disapprove, etc.) would have also made homosexuality or interracial sex "immoral" in 1950. Except for the illegality part, they might well make posting on RB "immoral" right now.
As long as both people are consenting adults, what they do is their own business. Yes, relatives or neighbors (or pastors or politicians or cops) might get uptight about it if they knew. So don't tell them.