These scientists could not publicly and unambiguously condone this for the fear of being singled out and picked out as "playing god" extremists.So they have to say the platitudes about "being careful" and ethical concerns.

However, when you suffer all your life from a genetic disease such as, say, the sickle cell or diabetes type 1, it is very obvious that it is any delay or hinderance in this direction that is deeply unethical, not the practice. Your germ line gets hundreds of random mutations at every conception, and your gamets get tons more mutations and errors as you age. It's not a dynasty hairloom.