Against,
If parents were able to "design" their children, then if anyone happened to be born the natural way, that would automatically put them in the lower rank of society. Thus, creating another way to discriminate against people.
Or,if only the rich were able to afford it, then people who couldn't would be outraged, and do something crazy.(I don't know what, but they would definitely do something.) Also, if the rich were the only ones who could afford it, then they would feel superior, creating more tension between people.