Human embryos edited to stop disease
I think there is far too much hysteria about this. We already operate on newborns to correct a thousand or more conditions. The only reason not to operate on a foetus is the risk of miscarriage.
So if we can avoid the utter misery of genetic defects which not only cause pain, and endless misery for the suffering, but blight siblings and the whole family - do it.
There are two main problems.
1) Abuse to select gender as there is still far too much cultural bias towards males. China now has such an imbalance due to selective abortion that huge numbers of males can't marry. For the majority, who are hetero this is a bad fate, and promotes rogue males.
But we already have systems to monitor this kind of abuse via foetus test & abortion, and such systems could be made stronger.
2) Long term implications as wiping out certain types of humanity* would be permanent, unlike blocking via abortion.
Serious defects are by definition undesirable and are highly unlikely to be helpful in terms of genetic diversity.
Less serious defects - harelip? for example, could be regulated so it stays as a post-birth op.
It really comes down to how we regulate, and how strictly - but whatever moral issue we consider, not just about this, will throw up borderline cases that push the boundaries. It's part of a human society to deal with this.
* Evolution depends up to a point on mutations which may have also some deleterious effects. The type of genetic engineering which is being considered may therefore prevent long term beneficial evolution. That doesn't mean that genetic engineering should be avoided at all cost, but the fact is that we are still too ignorant to fully understand the consequences of everything we try in the field of genetics. It's like life extending efforts. The longer we live the slower we evolve. Living very long and having few children may be a disaster rather than a blessing, as far as our long term evolution is concerned. We should be very careful about all these exciting possibilities.