"With incest it's different since vast majority of sex abuse of minors is incest-based. Real life incest is almost an equivalent of child abuse and rape. "
What's your source? You make pure affirmations without any argument or proof or source. This have no argumentative value. And you speak about pedophilia, not incest here. This argument is totally unrelated to incest betweeen consenting adults, i was advocating here.
Want to add a thing. There is some countries were incest is legal. If we search for criminal statistics on this countries, it shows that there isn't more abuse or rape on children case in this countries than in the one were incest is banned, that's mostly the contrary in fact. Link between incest and child abuse isn't proven, just like it was for homosexuality. That's prejudices.
We know only few cases of consenting adult incest because there isn't research on this. If we don't search we don't find. Also those people are hidding themselves cause incest is socially banned (even when that's legal). There were just the same arguments against masturbation or homosexuality just a half century ago.
I already answer on procreation and genetic problems. Incest make probablity (that's the important world, those diseases exist also for non incest pregrancies) of a rare genetic disease more important, cause those disease are recessive (they need two examplaries of the same bad allele to express). That's not like "all incest childs get disabilities", there is just a increase probability.
But sex isn't just procreation in our society (or you still live in the Middle Age). And we also know how to prevent those pregnancies: contraception,... Also we know whose gene are responsaible for those disease: just have to make preventive genetic tests (for all, not only incest couple). And in the case there is still a baby and he/she has those disease, there is abortion. So i don't see where the proble is, the argument is anachronic.
A study in Island (a country that study a lot incest cause they all are kin because of the small population and lack nof immigration) show statistically that in darwinian term (maximum life esperancy and maximum offsprings) the best is to date second cousin, not a stranger.
We are biologically wired to love people who are close to us, even genetically. thats what prove the studies on genetical sexual attraction:
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It was a taboo in some countries (mostly monotheists patriarcal countries, prohibition of incest probably start with judaism), not everywhere. I already site case of ancient egypt. In Persia and in the Steppes, mother child incest was consider sacred and zoroastrism have a large tolerance for all form of incest anyway. Incestuous (cousin mostly) marriage were common also in most area as a way to keep posession in the family, to not spread heritage. Noble families use it largely: for example, Alexander the Great's sister was married to her uncle. There was no such thing as universal prohibition of incest, anthropologists (Levi Strauss particularly) have been blinded by eurocentrism.
And for those who believe in the Bible, there were just Adam and Eve at the start, they say. So next generation, there necessary had a incest or humanity must have deseappears! There is also others case of incest in Bible, particularly the really disturbing case of Loth and his daughters.
Incest is also commun between animals. So that's not against nature.
I persist, i see no valid and rationnal argument for incest prohibition in knowday society.