Not slaughtered, nor killed, but not born, let their births be avoided, for their own good, it is a duty in my opinion. I would never want to inflict pain on anyone for no reason! The possibility of possibly causing someone to suffer is justice or revenge (or law of Talio), against a person who has been wicked, robbed, raped, burglarized, harassed, destroyed his neighbor, it is the principle of the punishment.
On the other hand, to procreate voluntarily, to have a disabled child, is to punish him "for free", to harm him, I would be mean to do that.
A person already born disabled, or healthy, or already born simply, will be the only one to decide for his own life, whether he wants to live, how to live, or, if not, leave life, at his convenience.
But, on the other hand, we can never ask if a person wants (or does not want) to be created, to be born, to exist, etc., it is simply impossible. Impossible because, paradoxically, we must already create it, give birth to it, wait for it to be conscious, to ask it this question! But, inevitably, paradoxically, it is already too late, she has already been born! So.
So, since, logically, no one asked to be born, we must make the effort to inflict (yes, inflict!) life on people but on condition of doing it equally, so that everyone can be born as equal as possible, so that everyone has exactly the same chances of succeeding in life, studying, living with dignity, having good parents, etc. I do not find it normal that we inflict, voluntarily in some way, on a minority of people (10% according to the UN of disabled people worldwide, 15% according to the WHO), procreation, disabled birth, harmful birth , a detrimental life!
You know, in some countries it is possible for a child, parent, to sue their parents, pediatricians, doctors, families, in court, obtain damages, in the name of harmful birth and harmful life. So, in fact, eugenics is justice, for the unborn. Other countries which do not allow such legal proceedings (the only alternative to eugenics) are imbecile, cruel, do not respect the victims of bad births! It's the same thing for countries that have not legalized CTB, euthanasia, and assisted suicide, it's cruel!