If they'd choose to do dysgenics, sure. Why though? Making a slave race?

Eugenics could be used ethically to improve humanity

Improving humans via new eugenics by transhumanists is compatible with human rights.

We allow natural mutation to produce illness and other problems. Why not design babies?

Gene editing will be cheap and widespread. What laws produce ethical results? Should personal eugenics be a human right? How about parental eugenics? Which baby designs are ethical? Don't say the current natural ones, because many of them are unhappy.

Misplacing the blame

Genocidal people having used eugenics as an excuse for mass murder doesn't make eugenics itself bad. Blaming eugenics does nothing to prevent further genocide with excuses. Hate does genocide, the various excuses do not.

(Similarly, over-optimistic fools slamming one version of communism on a whole country without prototyping different versions in villages first, crashing the whole country, doesn't make communism itself bad. Blaming communism does nothing to prevent foolhardy mistakes in societal change. Development should be nimble, prototypes should be cheap.)

We don't ban money because it's used to hurt people - we regulate dangerous stuff to protect human rights. Or, should regulate.

Eugenics works on animals:

Dogs have better social skills than wolves = eugenics.
Some dogs have trouble breathing = dysgenics.
Stray dogs in the wilderness are worse hunters than wolves = dysgenics in that environment.

Humans could be better:

Humans could be designed to work well in their lives:

• No disease, no ailment, unless asked for by patient candidate.
• Happy childhood in a family where everyone's personality is compatible with each other, DNA-matched.
  (can even be done by trading babies, without gene editing)
• Happy working career, DNA-matched.
  '

Humanity could be better:

Humanity could be designed to work well in its evolution:

• Better thinkers for avoiding disasters.
• Fewer born sociopaths, less risk of human extinction on purpose with future weapons.
• Fast adaptation to environmental changes, such as Mars colony in unhealthy 1/3 gravity.
• Better disaster survivability through species diversification.

Separate the human kinds from incompatibles

Echo chambers (countries, languages, professions) are cultures protecting their own environment from incompatible cultures. When a group of people demands seemingly absurd laws, they should be allowed to apply those laws to all volunteers, babies being non-volunteers with universal rights. At least personal eugenics should be legal, like body modification is now. Ear piercing is a modification some abhor.

Transhumans and conservatives need to stay away from each other, and current technology could help: phones could navigate people, routing incompatibles around like oil and water. On shared ground, weirdos would always happen to be on the other side of the street. Train cars and elevators filled with groups of people approximately their own kind. All cars good looking on every commute, timed just right for people's tastes. On the web, OkCupid and Quora used to be good at that, matching tastes and interests.

Do the opposite of what the for-profit sensationalist media does, smearing the wildest progressive stunts in the conservative's face, because rage sells, anger is addictive. The blame is mistakenly placed on the depicted, not the media breaking people's boundaries by pushing incompatible people into knowledge of each other.