The idea of Eugenics(selective breeding) has existed for thousands of years and probably before Plato even made the term. But it really took off and was popularised in the previous century, but subsequently quickly lost its popularity because of certain tragic events. The prominent arguments against eugenics nowadays are usually an ethical, religious or moral concern, but those are just hurdles which we have to overcome. We can see literal deformed lesser-humans or midget who are quite happy to spread their genes to further a sort of dwarf lineage, this is wrong. There is a reason the Hobbits hominids were wiped out, they were inferior, a lesser-human species. You can argue that natural selection will eventually take over and solve this, but is that really likely? In the coming generations, we'll see more midgets, more deformed and -or humans who are likely to spread certain faulty hereditary genes to their offspring. We do not mind our societies to take care of people who show abnormalities, but that is just sad. There is of no benefit in protecting those beings, not for humanity or anything worthwhile, rather they'll cause more harm in the future for our descendants to have to deal with.
nature.com
With new technologies which have made gene-editing easier by using viruses to edit the DNA of living organisms (CRISPER-Cas9), it has come to mind of many to use it on humans as it has shown success in other species of animals. I imagine our main goal in using this sort of technology is changing the Germline of the target so that we can minimize or eliminate the faulty genes which get's passed and replace them with acceptable ones, but first, it has to be improved and made cheaper. There are other options, such as simply making those in question infertile or popularise abortions in the 3rd world and instead of stigmatizing the practice we ought to talk of the benefit of such a thing.