Of the diseases you mentioned, Huntington's and CF are genetic, because they are caused by an error in a certain gene. Cancer, intelligence and behavior are not caused by genetic errors. They are the result of the interplay between genes and environment. So you need to be more specific in your sweeping generalizations.While we're at it, you should tell Stephen Hawking that his condition will send him to the gas chamber too.
As for violent crime...would you put a man top death for hitting his wife? He acted violently and had committed a crime. where do you draw the line on what constitutes violence and criminality? what about factors that often lead up to criminal behavior? How about drug addiction? It's a none risk factor. Should they be euthanized too? Statistically many of them will be involved in some form of criminal enterprise, some violent. Maybe society should just eliminate them all in deference to statistics.
IQ: so a spread of 20 points is enough to make one worthy or unworthy of parenthood? Which test gets administered? Who decides that? You? what if you score lowly, despite your grand ideas? Sorry, Perch. Too bad for you if the test is biased against your particular interests or abilities, or cultural background. Off with your balls.