I think you are quoting from the Book of Leviticus..
In the same book, if you are willing to read more carefully, it
also says that the eating of shrimps, sotong, clams, as forbidden..
So do u still eat those?
I guess at the end of the day, we will just need to understand the
principles between what's right and what's wrong. Instead of
following closely everything the Book has to say..
As for Incest, there's usually a "power" play.. e.g., mom and son,
father and daughter.. and the victims usually do not have power to
act against the pepretrator.. Hence, it's morally wrong..