Hi, I am graduating in biotechnology and my professors discussed this in class. The main points they brought up were:

1: the technique used for gene editing in those test subjects was and still is not 100% specific. With the correct primers you can still have incorrect breaks in the DNA and incorrect adhesion of your gene of interest, pair of bases can be lost and/or introduced indirectly, causing mutations that range from luckily encoding the same aminoacid to a sequence break, altering all of the following aminoacids and resulting in either a truncated protein that luckily does nothing to a protein that results in who knows what damage to the cell. This is ok in situations where you're changing just a few calls inside or outside of the body, but when you're changing the genome of an entire person, that is extremely dangerous for no real gain because

2: the gene he edited was still being studied and was not guaranteed to give them immunity and it turned out they didn't gain immunity to HIV.

3: there are better ways to guarantee a baby is not born with HIV that are better known, do not involve possibly giving ultra cancer to babies and have been throughout tested before, they did not advance our scientific knowledge and put people's lives in danger for no guaranteed benefit besides his own ego.

There's a reason why the entire scientific community was against his actions, especially those who work with genetic editing.