While I am at it, here are two comments I left at Will Saletan's Slate article on why incest is wrong. He seems to think that we have to identify the single reason that can make incest wrong which doesn't apply to homosexuality. I disagreed with that requirement, and asked him to address procreation rights of fathers and daughters:
Hey Will, can you do an article on the procreation rights of fathers and daughters, as opposed to the naked/orgasm/screwing rights? (Well, perhaps you could look at those three separately too, since they are rather different.) For instance, would it be a crime for a daughter to impregnate herself with a vial of her father's sperm? Is it something we have to allow a father and daughter to do, if they wants to?
And, how about the marriage rights of fathers and daughters? I think that the procreation rights and marriage rights of fathers and daughters are synonymous. Indeed the Massachusetts Incest law has one paragraph describing the crime and punishment that applies interchangeably to either sexual intercourse or marriage (which of course would have to have been an unlicensed illegal marriage, since such a marriage is also prohibited by the marriage statutes). Interesting how that shows marriage means having sexual intercourse as far as the public understanding of marriage goes. It also means having children together.
How come there can't be multiple reasons that, taken as a whole, call for incest to be illegal and wrong? Not everyone agrees that procreation is not an issue between fathers and daughters, that's pretty ballsy to just say that unethical procreation is not an issue because now we have contraception. As if that somehow makes it impossible for a father to impregnate his daughter! Or a brother to impregnate a sister, or aunt, etc... There are also other reasons to criminalize bodily union between relatives, as well as to not allow marriage between them. (And there are reasons why affinity relationships that are prohibited from marrying are not criminalized and punished the same as consanguineous relationships are.)
The "family unit" reason is a reasonable reason too, as is the "impossible consent due to grooming" reasons. Not everyone has to agree on the reason they think incest should be a crime and is wrong, there just have to be enough people that agree it should be a crime to say it should be a crime. They don't have to all agree as to what is "the" reason that holds true in every case and is logically consistent with marriage or gay rights or feminism or whatever, they can just feel there might be good reasons to prudently prohibit it.