We have mostly managed to get past that with the realization that we are all human. Now you want to "turn off" what makes us human. You want to remove the "soul" if you will. But the problem is that unless you know what it is you can not turn it off and I doubt that there is even an off switch.
So what you want is to create a human that is just different enough from you that you can justify killing it to yourself.
How does this connect to killing the disabled? Because I hear those same rationalizations from those who advocate killing them for their organs or using them in experiments.
They don't see them as human. You want to make clone that is disabled so it won't be human.