One of the more pernicious aspects of this debate is that talking about it without being labelled a luddite is difficult. However, there are several practical concerns about He's work that were raised by geneticists.
The first and most obvious one is simple, we don't actually know if the changes worked. Unless He were to introduce HIV to these children, we don't know what their "immunity" is, and we don't know to what extent it would be conferred,
> The key takeaway is that CCR532 does not guarantee immunity to HIV infection and possible death. It only works for strains of HIV-1 that use only CCR5 as a co-factor along with CD4 to infect T cells. A few reporters seem to have noticed, or at least commented, on the importance of CXCR4, including early news stories from the ATLANTIC, NATURE, and BLOOMBERG.
But those facts then disappeared probably because ‘complete’ protection against HIV infection made for a better story, a better dilemma, and a better thought experiment, even though that it did not match the reality of the situation for the two baby girls.
https://academic.oup.com/jlb/article/6/1/111/5549624?login=t...
Once you understand this, Mr. He is less of a heroic Prometheus, and more of a meek, milquetoast Josef Mengele, conducting unethical experiments badly at a much, much smaller scale but with possibly greater fallout (from a very narrow perspective - I do not wish to make light of the loss of life that Mengele's experiments led to nor the suffering he brought onto others. I am talking about the cross-generational effects of what He has done.).
The second fact that no one has talked about is that we don't actually know how the changes will be expressed in their bodies and how they will be spread. More bluntly, CRISPR is an amazing tool that is sharper than anything we've had, but it is still fairly coarse. There are several "off-target effects". A bioethics statement in Nature stated as much,
> Third, reporting of off-target effects and highlighting of the risks of gene-editing embryos was insufficient. Off-target and undesirable ‘on-target’ effects are common- place with the use of CRISPR–Cas9 and represent the most prevalent risks to an organ- ism. He acknowledged such risks in his pub- lic statements but falsely reports that he has determined how to eliminate them or interpret them as irrelevant to the functioning organism.
https://sites.tufts.edu/sheldonkrimsky/files/2019/01/pub2019...
We have assigned it far greater precision and ability to propagate changes than it actually does. It's also rather easy to mess up. So we don't actually know if these changes were propagated to all of the cells of the blastocyst. We don't know how they will be expressed and we don't know what will happen.
> Any unintended and deeply uncertain improvements in the cognition of the twins cannot be counted as a benefit in an ethical assessment of He’s experiment. Quite the opposite: the possibility of any brain effects should be considered yet another risk of the work.
> What about the benefits to science? The fact that apparently healthy children could be born after embryo editing is, certainly, a novel finding of some value. Given earlier successes with monkeys, as well as other mammals, it is not deeply surprising—but nei- ther was it completely certain. Even closely-related species sometimes differ markedly in reproduction and early development.
Indeed what those studies have taught us is that these tools are still too primitive for such discussons.
What makes this more horrifying is that by doing this, He has altered all future descendants of these girls towards unknown ends without informed consent. In effect, this experiment is not just upon the current generation, but all future generations as the germlines have been edited in, frankly, not-well understood ways.
People outside the field who discuss the topic by talking about the stratification of the rich and the poor etc. are discussing a valid concern. But the real concern is that we aren't there yet. This is a blunt instrument that has been used to change all the future descendants of these children, without any regard or understanding for what will happen or what has already happened.
What do we do now? Prevent these kids from having children a few decades from now? Is that fair to the children?
He and all parties involved have left a mess for the world to clean up.