I think eugenics is a stupid idea. As a species, non favorable genetic mutations are a dead end anyway. Let us suppose we could objectively quantify a gene as good or bad and select only for the good genes by whatever means are employed. In that case, we'd not do anything else as nature does anyway without our doing, so eugenics from a biological point of view is pretty moot.
Another, far more concrete problem with eugenics is that genetic traits are (most of the time) neither good nor bad. Any genetic trait with significant prevalence in the population is there for some reason, and removing that trait drains a much needed genetic diversity. A famous example for such a trait would be sickle cell anemia, which actually infers resistance to malaria. Where is the gene most prevalent? In tropical Africa. Bad traits are always self limiting, and only traits that offer some advantage get selected. Nature does that without our interference, and we can only cause harm by trying to meddling with diversity.
Most species that had their genetic diversity reduced too strongly are now extinct or are having serious disease problems.
Now, one needs to differ. Yes, there are traits that cause an undue burden on families, such as Down's. Disease burden is a quantifiable parameter, and I think that every family should be able to decide whether or not to endure such an undue burden.
The governments however also need to regulate genetic screenings in order to prevent selective abortions based on hair colour/sex etc. Only traits that cause a certain threshold of burden should be screened for.
Another point that can be raised is the healthcare costs associated to genetic diseases such as Down's. Yes, they cause costs. And in comparison to obesity/smoking related costs, they are wholly insignificant. The loss of perceived freedom and associated mental problem costs (long term stress is a real killer) with a regulation of such traits would probably topple the cost of healthcare for the traits themselves.
And besides, ultimately any non violent death could be prevented with the right trait. But then again, sometimes traits are sometimes exclusive, interfering with each other or whatnot. We could probably engineer, after sufficient deliberation, a genetic code for the human being that serves as a background for a healthy and long life. Selecting for that model would however be contrary to natural selection, as our genetic diversity would crumble and destroy our species.
Also, we got an entirely different approach in dealing with diseases. It's called medicine. In a way, drugs are an extension of our genetic code and offer a far more elegant and easy way in dealing with faulty genetic traits. I believe that medical and scientific progress will, as it has done in the last centuries, offer a far bigger advantage to human health (as a species as well) than any eugenics program ever could.
