Any more than the emotional exploitation and abuse that takes place in non-incestuous couples?
Absolutely. "Incest", by definition, indicates sexual relationships among family members. Even if these are limited to consenting adults, the fact that it is accepted at all implies acceptance before adulthood, or between adults and offspring. We are all far more vulnerable to manipulation and abuse from family members than from outsiders. So to allow incest, even just among connecting adults, I believe would dramatically increase the likelihood of emotional and sexual exploitation and abuse among family members of any age.
Is there a certain level of acceptable risk of birth defects, below which we "allow" people to reproduce? Surely there are non-incestuous couples that, due to the genes or behaviors of one or both members, bear just as great a risk of birth defect. Yet we do not ban their marriages.
Yes, which is why I would not base such a decision on the probability of birth defects, alone. But in conjunction with the increased likelihood of sexual exploitation and abuse within families, I would be comfortable discouraging it in general. However, when it came to the rule of law, we would probably want to stipulate instances in which it may not be prosecuted.
And of course there's the horrendous truth that, in a legal system fully accepting of contraception and abortion, risks of birth defects make for a weak legal argument.
Not really, because it would be nearly impossible to make a law forcing an incestuous pregnancy to be aborted. Which means the abortion issue would have no applicable bearing on the incest issue.
