The ability to modify our children would not come without a hefty price tag on it.
The individual arguing against my previous statement of preserving natural selection would state that it is immoral to not use the technology available to at least prevent life threatening and life altering diseases. Being that is a reasonable statement, another argument that would come up would be, at what price? The rich and the poor population of America is already separated by their income. With the rich having the ability to choose the genetic traits of children and those who cannot afford it would not, there would also be further isolation of the poorer population.
They would consistently become sick and be prone to catching super-bugs that are now evolving due to a certain population being completely immune. With the ability to choose the shape and the physical traits of children, there would be further separation between the rich and the poor. This isolation would stem for generations, giving the poor less chance to achieve a feasibly happy and successful life. In the past there have been politicians that attempted to change the genetic trait of the population by forcing the citizens with the appropriate genetic traits to reproduce with another person that has the desired trait. One recent example of a politician who attempted to completely revamp the trait of his population is Hitler. He envisioned the German population to be tall, blonde hair, and blue eyes.
Those with any genetic defect, including children with Down syndrome would be immediately killed. Those that do not have any of the desired trait, as seen in the book Maus by American cartoonist Art Spiegelman, would be consistently harassed, tortured, and sent into concentration camps. With increased usage of the technology to change the genetic traits of our children, there would come an increase amount of politicians with their own set of rules on how their country should look like. There would be consistent harassment of their citizens to upkeep the look. Genetic variation could potentially be lost, or there would be an increased amount of racism based on how an individual looks.
There would be armies of super-humans built to not only protect the country, but to attack a poorer country that is unable to afford the technology. Children would be born with specific traits for a certain type of job in the country and would not be able to decide anything else for themselves.