Potential children are in abundant supply and the world is overpopulated with people without a future. Every child brought into this world should be of the finest intellect possible, and free of genetic diseases or abnormalities.
Every generation needs to be an incremental step in the evolution to a new species.
Other behavioral traits must only be altered when there is no longer a danger from competitive species and our knowledge of our species has progressed to a state of understanding that makes behavioral traits modification beyond question. Until then, we must retain the full spectrum of human variation for the sake of higher adaptability and survivability. It is practically impossible, and undesirable, to enhance via selection all or a lot of traits that vary in humans. The traits that need to be enhanced are those that have a relatively universal and absolute value, especially as far as the group's strategy is concerned. I can think of three traits that have this importance.