Why shouldn't the parents get to choose? It's going to be their baby, their responsibility. They're the ones who are going to be paying for gender sorting, the pregnancy, and the baby once it gets here. They have to raise, pay for, and love the damn thing, why not not make it a little bit easier on them by letting them get the gender they want the first time instead of trying six times for a girl and ending up with six boys (or vice-versa)? Also, many genetic diseases have higher/lower occurrences in one gender over the other (Myhre syndrome is more common in females, hemophilia is more common in males, etc.) Giving parents the opportunity to have the gender they want and possibly prevent them from the heartache of a severely disabled child can only be a decent thing in my opinion.
Laws regarding reproductive rights are basically unenforceable and senseless. If parents could pre-choose the sex of their child, it would be through the work of science and medicine combining to create a genetic modification. Pre-selection might be a good thing for some parents, so this option should be kept open. Parents will always be responsible for their children, no matter what gender they are.
Parents may think that they want a child of a particular sex, but in reality, they have no way of knowing what that child's personality may be. If the parents are allowed to perform this type of eugenics, it is only a small step toward selecting against children with genetic or physical defects or any other type of potential health problems. This is a dangerous step toward Hitler's concept of an Aryan Uber-race.