I think the ethical question is more along the lines of whether or not certain people should be able to alter the genetic makeup of their children to make them "better" than other humans. Imagine this: in the future, there is a clinic where you can create your own "designer baby." The process is expensive, so only the wealthy can afford the service, while others must rely on the random, natural method of child production, which can result in harmful mutations and disorders. Relating to evolution and natural selection, in a sense, this scenario brings up the concern that the privileged may be able to have children more suited to their environment. For instance, they could be genetically engineered to be healthier, more intelligent, etc., giving them an advantage over the children of those who cannot afford gene modification.
Of course, this is just hypothetical, but the technology to alter genetics is real.