not all "bioetchics hand-wringers" are against gene therapy ( in fact you too are taking a bioethical stance).
bio-ethicists aren't only interested in the net good of the patient of the therapy, but also in any harms onto others: perhaps child victims of organ trade (for example sourcing fibroblast stem cells from unnecessary circumcision of infants), perhaps harvesting organs from political, cultural or criminal prisoners, or from refugees, and yes, some of them are worried about viruses ...
bio-ethicists aren't only interested in the net good of the patient of the therapy, but also in any harms onto others: perhaps child victims of organ trade (for example sourcing fibroblast stem cells from unnecessary circumcision of infants), perhaps harvesting organs from political, cultural or criminal prisoners, or from refugees, and yes, some of them are worried about viruses ...