I tend to get cursed at when I try but if you'd like:
I don't think euthanasia or sterilization or anything like that is okay in the context presented. I personally do lots of volunteering with mentally handicapped children and I think they are sensitive and beautiful and I cannot fathom getting rid of them because they may not be able add anything scientifically or philosophically etc to society. They teach compassion and empathy and make one question their own worthiness of what they have and compel one to maximize what with what they have. Besides this, works of irreplaceable art have been made by people with mental handicaps, for example http://www.amazon.com/The-Reason-Jump-Thirteen-Year-Old-Autism/dp/0812994868
not wtf if you get this and read it. explains a lot
http://www.amazon.com/The-Reason-Jump-Thirteen-Year-Old-Autism/dp/0812994868