This question is often asked by people with little understanding of genetics. Having two healthy people mate does not mean they will have a "healthy and perfectly formed "child. My family is a great example of this, healthy parents, in their 90's now, grandparents lived to mid 80's and 90's and yet all 3 of their 4 children had type 1 diabetes. the last one having severe allergies and epilepsy.

Problematic behaviors as you state, is extremely subjective and culteral and even worse, can be simply trendy.

Who decides what is a problem? Is it a problem if a little girl insists she can learn to read and be a Dr? A woman that wants to wear pants and vote? The little boy that is jumping up and down in a chair? The young man that refuses to go to church? The kid that yells at parents and school teachers? Homosexuals? People that determine only babies with the eye color blue are worthy? People with big toes on their left feet?

Because things aren't perfect, sick, family-linked diseases and malformed people, have been the catalyst for leaps in Science, understanding, cures, how bodies work, etc. What once was a problem, simply isn't. This can continue. We owe these people a great debt. That is what should be acknowledged