He got downvoted for implying that only a mentally handicapped person would ever be a grocery store bagger. I used to work front line at Kroger over summer break, I know some pretty great people who still make a living that way, and I don't appreciate the insult.

Down's is already 'prevented' in many cases, as the statistics for abortion of Down's fetuses detected in utero show. Many with Down's can live rather full lives, as some have rather mild differences in mental state than neurotypical peers. Many participate in school without the need for extensive supports, and function in work situations. There is a bit of a range in the abilities of those with Down's.

There are other diseases that can be managed in a way that minimizes the impact on quality of life. It's still preferable to prevent them.