I'm all for gene modding and designer babies. I think the fears that allowing some gene modding will open the door to all gene modification are pretty legitimate though. Also, I believe it will create a huge probably with class issues, since wealth gap and all its benefits will widen to include evolutionary advantages on a reproductive level.
Get rich -> design your babies to be brilliant and athletic without any genetic diseases -> pay for best schooling available-> Kids become successful -> Get rich -> ....
That all said, I think trying to stop it is just delaying the inevitable. Some people will be disenfranchised, but hey, evolution is simply too slow for us to wait around for. Outlawing the practice might work for a few generations, but at some point the rich and powerful will circumvent the laws and the effect will be the same. The world has seen some rough times recently and it ain't just going to get better all on its own. Maybe through our genetic manipulations we'll accidentally (or purposely) create really empathetic rich/powerful people who will legitimately help the world/people.... Or maybe future humans will just be Inchoroi.
Either way, what we're doing now really isn't getting us anywhere where we want to be, lets continue to try new things and use science to our advantage. Running in fear from our own discoveries won't solve anything. Sure, the discovery of nuclear power first led to Nukes, but its also led us to fission power plants, and will eventually lead us to clean fusion energy. People aren't very good at doing the "right" thing, but eventually it works out.