Eugenics/Designer-babies... is the concept really that bad?

[Aoi Magi]

At work today, the topic of gene editing to alter fetuses came up, and most of my colleagues seemed to be strictly against that, but I really don't understand why. Sure if an error goes out into the population unchecked, it can lead to totally unpredictable consequences, but if I am not mistaken, evolution does that all the time already, at least if we take control of the process ourselves we might have a chance of fixing things before things get out of hand. Also, evolution is damn slow and unpredictable and hence unreliable for our survival. I mean, let's say our blue planet is hit by another large space rock, can we really say we will be able to evolve and adapt in time to survive the planet-wide changes? On the other hand, if we by then have properly mastered our genetics, we can easily engineer our offsprings to survive the disaster. Moreover, if we can engineer ourselves to survive in space, then I don't see any reason not to try it, we will be able to colonize other planets easily and ensure our survival. Also, I know that those kinds of engineering capabilities are decades, if not centuries away, but if we don't take some tiny risks and start studying now, how can we ever expect to get there?