The unwanted severely retarded
So you are willing to support these people into old age with all the medical care that they require: feeding, watering, dusting once a week?
Fine. Set up a foundation. Or put a gun to Tom's head and use tax money.
Severe retardation is sometimes diagnosed before birth and abortion is sometimes the treatment. Do you want to take that prerogative away from the family? Are you willing to take over the care of that person, once born, for 60 years or so, or do you want to force the family to do it?