embryos are not people. Unless everyone has suddenly turned into an enthusiastic pro-lifer it seems bizarre to me why destruction or termination of children with genetic defects is supposedly ethical, but trying to prevent them is not.

By definition unborn children or infants cannot give consent. That has never been the basis for denying them medical treatment, including experimental ones. And in the entire history of medicine no established treatment exists without experimentation.

If this is even remotely successful you may be looking at millions of lives saved by preventative HIV treatment in regions where the disease still kills millions.

A 40 year old woman getting pregnant probably poses higher risks for their offspring than a lot of genetic experimentation. Is there any risk basis for these arguments or are people just apprehensive about gene-editing due to some naturalistic dogma?

Just to think through this, people with Huntington's can, with a 50% chance, bring kids into the world who are doomed to basically die of a horrific disease, that's considered the personal right of parents. But the same parents couldn't subject some cells to treatment to attempt to prevent this, that's unethical?