Inevitable next step after this would logically be designer babies.
That's not even a slippery slope. That's genuinely what's going to happen. There are going to be companies which do this on a private basis, and they will allow people to change how their babies look for a high cost. That will, in turn, lead to an even larger gap between the rich and the poor, where the rich are far smarter than the poor due to being able to edit their genetics. This difference will eventually compound until the whole of society bursts. This is not just a small thing.
Also, you can't trust people with that, which isn't lethal. Since this does not actually harm anybody, editing the MVO, people will do it. People's moral compass won't stop them from editing. The kid to look perfect will be genetically perfect. In fact, there will be experiments conducted. There will be a perfect human created. All of this will lead to the loss of humanity, because what is humanity if not the sum of our emotions and flaws?
12:09 AM