Aldous Huxley in Brave New World gave us an enduring image of a world full of designer humans. We can look back patronisingly on the nazi eugenics campaign that saw mass sterilisations and so forth, on the "quaint" notions of Aryan purity that still, "quaintly", fuel the imaginations of our white supremacists, our skinheads, our KKK and the like.
We are not, historically speaking, all that far removed from attitudes that saw non-Europeans - and women, for that matter - as "lesser breeds without the law", attitudes that sanctioned slavery and child labour, attitudes that allowed Bulldog Drummond in one of his fictional adventures to thrash a "jewboy" with a rhinoceros-hide whip "because he probably deserved it."
We are not removed at all from an attitude that sees humanity at large as widely capable of genetic "improvement".
Years before GE, Rex Fairburn caught the mood:
...Young Jack, a surgeon fresh from college
Held life synonymous with knowledge
And, knife in hand, with small compunction
Explored the function of a function...
This is not to say that all scientists are arrogant, or that no scientists at all have shown a sense of the fundamental dignity of human beings or indeed of life itself. Just to say that these notions of intrinsic dignity and worth are ours to preserve or discard, and that we shall inevitably live with the consequences.