I have some pretty strong feelings about eugenics (it's a good and necessary practice), but I find it very, VERY difficult to talk about it with anyone since I'm instantly labeled a Nazi for supporting it. I'm hoping the folks on Think Atheist will be more inclined to intellectual discussion than name-calling and dismissal.
The start off, some disclaimers: genocide is wrong; taking human rights away from people of a race/religion/hairstyle you don't like is wrong; concentration camps are wrong; violence in wrong.
There. Now to the actual discussion.
When I talk about eugenics, I'm talking about the practice of systematically removing debilitating genetic traits and defects from a population by means of regulating the reproduction of its citizens. Do you have Schizophrenia? Did you know that this ailment is genetic and very easy to pass on to you children? Please, do not punish an innocent child with this problem. Are you genetically healthy, intelligent, and talented? Do you have special immunities that make you less likely to get sick? By all means, spread these traits to future generations, either by having children yourself or donating to a sperm or egg bank. Do you want children but should not carry your genetic problems onto them? Adopt. Adoption will always be available no matter what the society (just because someone has good genetic material does NOT mean they would make a good parent). Do you say that adoption is not the same? Then I suppose you care more about satisfying your selfish desires than the well being of a child.
Eugenics is, at its base, very simple - think about the future first.
I'm leaving this post now for what I'm hoping will be thoughtful and anti-inflammatory discussion.
I like science in general. It all holds my attention. I loved Carl Sagan best I would say. But, as this isn't really on topic...I'll return to the point that you, as one person cannot measure the effect one person has upon others. Just because someone doesn't personally enjoy the aura of Hawking doesn't mean he hasn't effected others.
Also, if this discussion is taking a turn toward determining human value of one sort or another, then it will be easy to then start looking at IQ, behavior, etc. and the idea of euthanizing problematic people becomes very easy. This is partly why the ethics bring us around to the decision that eugenics is not a wise or viable solution to anything.
What is the value in not doing so... ???
I'm 45, I see the cycles of life go by. I get very frustrated that nothing is ever new, we keep doing the same crummy behaviours as our predecessors. No battle (social, environmental) is ever won in the long term, nothing is ever truly gained. On daily news we keep hearing these "new" discoveries which have been around for 30 years. We keep trying to redefine the wheel. The youthful mind will never accept the achievements of the preceding generations. So from generation to generation, the personal wisdoms of life are lost. New generations want to define themselves, not be defined by the "old foggies".
Our present society's knowledge base is not "personal" but "institutional". If we were to have a major social collapse due to disease or catastrophe, most knowledge would vanish as it's not in the realm of one person's mind. Modern humans live outside ourselves, completely reliant on energy driven technology for our survival. I compare this to the little island in the bay across from where I grew up. This island was inhabited between the 1800s and 1960s. The people there didn't even notice when the great depression rolled through North America, because they were completely self-reliant and their knowledge of life was appropriate for their survival. They were happy, until television came along and everyone began to dream of being rich "like Americans".
In nature animals do not generally reach menopause. I consider life is for the youthful. I have zero interest in long life. Society's obsession with eternal life is pure gadgetry in my eyes.
The reason I'm for eugenics from the filtering standpoint is related to this 'natural' limitation. Humans can be quite happy without gadgets. Limits create value. Without limits, there is no value. It is a fundamental principal of value, rarity creates value.
I have several arguments to the above:
 We are living in an age where technological transformations have been massive. "New" discoveries have abounded - computers and information theory are less than a century old and have completely redefined humanity.
 Social battles are won. The increasing rights of women with regards to family-planning, education and equality are an example.
 Environmental battles are won. One quarter of my civil engineering degree consisted of environmental law, engineering, and social studies. This was not the case in engineering a century ago.
 Most human knowledge would not disappear because we will not unlearn reading or writing, the two most significant tools we have developed. Humanity would be vastly impoverished if we returned to this state.
 Rarity is also known as scarcity, one of the drivers of price manipulation (see oil). Rarity is not necessarily a good thing.
I do agree with the following, though:
 We always lose social knowledge at each generation. It despairs me that this is not better integrated into school education, as it is fundamental to our development.
 Technological uplifting does not improve happiness. Television has not increased the happiness of the average child. As an extension, longer lives will not improve happiness.
 Globalisation has made every part of the world sensitive to events out of their control. This was, however, inevitable.
"Television has not increased the happiness of the average child."
There was actually a study in India, refrenced in Superfreakonomics, suggesting that the introduction of TV has led to substantially lower reproduction and domestic abuse rates. Presumably that increases happiness of the average child since they will receive more nourishment, education-by-TV (vs no education), and don't have to watch their mothers being used as punching bags (as often).
TV isn't all bad, but I wouldn't mind if Jersey Shore was banned by law as polluting society's environment, and all which could be legally aired were properly peer reviewed documentaries. ;)
Imagine Stephen Hawking's motor neuron disease was identified and corrected before he was born. He would not have had to cope with it. He would most likely have a greater number of productive working years (he has overcome a great many difficulties to work, but if he did not have to he could probably work harder, longer than he does. Which is what many a scientist desires). His quality of life would be greater than it could be with any current treatment.
It is not saying he has less value as a person NOW because of it. Nonsense. You are not valued because of your wins and losses in the genetic lottery.
"And, how about people like Stephen Hawking?"
And how about Cell lump X, which would have cured cancer, but was aborted? You don't know a priori who will become a great contributor to humanity, and it is not a valid counter.
"If a woman chooses to abort for whatever reason she sees fit, so be it."
Now you are going completely overboard with womens right to choose. If she has a special priviledge without associated responsibility, then there's plenty of room in the forest to give birth. Individual rights come with individual responsibilities.
"But to systematically decide what constitutes a viable person based on what diseases they may have...this is dubious."
Less dubios than letting women choose completely at their own volition just because they happen to have been born with ovaries. And who's got the right to choose if we one day find a way to make babies ex-utero, progress seem to be closing in on that one quite quickly.
"I maintain, if you want to improve quality of life for all people, teach and educate."
Parkinsons and senility run in my family. Please educate me how I can be assured I will never be the victim.
"about the fact that several genetic diseases are on the rise and yet the increase cannot be explained by reproductive measures."
Usually these become apparent because we have greatly extended life expectancy. With added time, nature finally kills us off. A couple of hundred years ago, women had substantially shorter life expectancy than men. Most died in child birth, most before the age of 25. Most children died before the age of 10. Advocating anything remotely similar to such a system offends my sensitivites, as they should yours.
I am a supporter of a woman having full reproductive rights. I am not going to argue that here right now. I did not suggest it was without responsibility. Having babies "ex-utero" is not what I am discussing and raises a whole set of other ethical questions and problems. For the matter of that, I am not in this thread to argue reproductive rights with anyone. It was a point with a means to help explain my other point of view and not there to open up a completely different topic.
I'll start here: Celiac disease is genetically marked and yet scientists cannot explain why its prevalence is doubling every fifteen years since they started keeping track in the early 70s. Their current belief is that something environmental is acting upon us to cause this. Celiac disease is not a disease of old age, nor middle age.
Diabetes Type 2 is at epidemic levels. Any site you visit: Mayo clinic, WebMD, Kaiser will recommend specific dietary changes and exercise. I am not sure what study you are referencing...a link would help. Read, "The China Study" which supports that diet and exercise prevent and treat that and multiple other diseases. Fact is...bring a rural Chinese or other person consuming a largely plant-based diet to this country or to the main cities and feed them a western diet, they too will develop "western" diseases. Again: show me a person's diet and I will tell you whether it is likely causing their condition.
In regard to your question about Parkinsons: I am now curious to do a little research on this question. What I did find with a quick poke around is that industrialised countries have a far greater prevalence...cause unclear. Smoking and avoidance of heavy metal toxins and pesticides are preventative.
Remarks regarding life expectancy ignore several facts. The belief about us living longer is a little bit misguided. Our capacity to live the length we live has not changed. What has changed is hygiene (preventing a very high death rate in newborns and women), immunizations, and modern surgical methods. The mean will jump strongly if we stop eating garbage and pretending it's food.
We have more power over ourselves than people believe and perhaps our lack of belief in our own health and future is tainted by the commercialization in our culture and the perpetuation of lack of free will by various religious dogmas.
Also, in response to your comments regarding migraines. I have had them my entire life. My last one that lasted more than one day (2 weeks is how long it lasted) was last November. I now only get 2 per month maximum that last less than one day and have minimal intensity. How did I change this and several other health problems? Diet and diet alone. I'm still working on it and determined to eliminate them altogether. I have never been healthier and I'm still working on it. If the argument for eugenics is to improve quality of life, we are missing several easy and cheap ways to vastly improve quality of life. Let's start simple and see if the desire to engage in ethically unbalanced practices fade away.