I just want to double check something with LWers.

Incest among adults is also sex between consenting adults. At least some such relationships are happy ones. Most arguments against incest are arguments where the bottom line is already written since they are made by people who just don't want to admit they are plain grossed out by it. Not only the motivation, but many of the arguments are basically the same as arguments in favour of homophobia. If the person has an identity centred on fighting "bigotry" cognitive dissonance hilarity ensues.

Bonus round: Arguments against incestuous couples having children is a fundamentally eugenicist argument. Applying it like a consequentalist results in concluding many other kinds of couples should be discouraged just as much (perhaps even with imprisonment since that is the price of discovered incest in many countries) or incest being legalized.

German incest couple lose rights ruling

The ECHR said the main basis of punishment for incestuous relationships was “the protection of marriage and the family”, and because it blurs family roles.

It also noted “the risk of significant damage” to children born of such a relationship.