I get your concern (this is the first time I'm hearing about it and oof). I would however point out that the core of transhumanism is the idea that we should have the freedom to modify our own bodies however we want. This is how I've always heard it used and how I'm going to keep using it.

I do understand where those people are coming from, though. If you have the technology to e.g. eliminate sickle cell anemia and choose not to do it, that's as much eugenics as choosing to do so. I don't know how to square that with individual liberty. Having parents decide is....not necessarily a great solution. Having society decide is also not a good solution, but probably the one we'll have to end up doing.