I was thinking about the moral problem of breeding couples with heritable diseases, specifically bipolar disorder (since I have it), and I came upon a nice little analogy that is pretty damning to those who think it's ever OK for two genetically-impaired parents to have a kid:
First of all (this isn't very well-researched, just Wiki, but it's a start), bipolar disorder has a 0.4% lifetime suicide rate among all patients, and a full third of them attempt suicide at some point. Those numbers compare well with the mortality rate and general seriousness of West Nile Virus. For those who don't know, West Nile Virus has to be handled in level 3 biosafety labs, right along with a bunch of shit the Pentagon tried to turn into biological weapons. You Do Not Want West Nile Virus.
So let's think of a couple where there is a decent chance of passing on bipolar disorder to their child. They have it, everyone comes to the baby shower, and they wish them well and give them lots of nice presents. It's a joyous occasion, and the parents may even be praised for their decision to reproduce. People might know about the parents' heritable genetic problem, but surely they would smile and nod anyway.
Now think of a genetic supercouple with no possibility of passing on a hereditary illness to their offspring. They go to the hospital, the child is delivered, and just as it comes out of the mother, the father sprays it in the face with a spray bottle full of West Nile Virus. Wanna know what happens?
Go to jail. Go directly to jail. Do not pass Go. Do not collect $200.
Oh, and also, you're going to be on the news for months, you will never live down your infamy, and you are never going to see your kid again, ever, regardless of whether or not it manifests symptoms.
I just don't see how willingly conceiving a child with a known risk of severe lifetime disease differs from willingly conceiving a child with no risk of severe disease, then willingly exposing it to such a risk later. You're deliberately gambling with someone's life in a way that goes far above and beyond the usual case for philanthropic antinatalism. I think this shows just how far toxic cheeriness infects our society. It warps all our perceptions and allows us to get away with assault/manslaughter/criminal negligence, as long as *our* genes do the hurting and not genes from some mosquito virus.
Intuitively, it does seem that we treat the risks inherent in the creation of a child differently from the risks we expose a child to after he has been created. This is true even though different prospective parents expose their children to different levels of genetic and early developmental risk.
The explanations I find most compelling for the double standard here are, first, an ill-thought-out, pluralistic/liberal distrust of eugenics, and, second, the very abstractness of the harm, compared to, say, kicking a baby like a ball or microwaving her.
And, of course, there's the idea that any existence is better than none, so that any risk necessarily engendered by bringing someone into existence is acceptable, whereas creating new risk after the fact is morally questionable.
What other reasons might there be for treating genetic and early developmental harm/risk differently from the harm/risk created later in a child's life? Is it so obvious that any existence is better than none? This seems like a dubious proposition upon which to base such a a serious action as childbearing.
On the Nazi/eugenics issue, I think it is highly relevant that many observant Ashkenazim participate in voluntary screening for Tay-Sachs disease. This, despite speculation that heterozygosity confers greater intelligence. As a culture, observant Ashkenazim have decided that the suffering of children born with Tay-Sachs is more important than concerns about "eugenics," and certainly more important than a speculated slight increase in intelligence for carriers.