I think the answers you are getting to your question on incest are one-sided.
I agree that incest is much large than is admitted, having several friends that have participated in it. However, it is not likely for someone who has suffered because of it to answer to your question because of the shame they feel.
I will tell you about one of my friends. Her father is a Minister at a Methodist church. She has two brothers who are older than her. Her father started molesting the brothers at an early age (not sure when). They believed it to be OK since their father did it to them, so they both tried it out on her (my friend). For 7 years her brothers continued their incest. She even had an abortion at age 13-14 because of her brothers. She told the authorities, teachers, and doctors.. all knew, but never followed up on it. She was one person who did not find incest positive. She has been institutionalized several times for depression and other problems. She sees life as a living hell. Please add this with your postings in the newsgroups, because it is a side that needs to be told.
I Am not condemning it…
I have not personally experienced it, but I have seen several results of it->none of which are good.