To make this point, we have to argue that the needs of society outweigh the rights of the individual. 

In the United States, we feel that the choice of whether to have children is an intensely personal choice.  We do not think that the government should play any role in this choice.  Therefore, an argument for such intervention must argue that this point of view is less valid.

The best way to do this is to argue that people do not have the right to place a burden on society.  We could point out that a child with a genetic disorder is likely to impose costs on the rest of society.  It is therefore not only a personal choice.  A child with a disorder will need much more medical attention.  This will impose costs on whoever is paying the person’s insurance.  All the other people who buy from their insurance company, for example, might have to pay higher premiums as a result.  If the person is employed by the government, taxpayers end up paying more to subsidize the person’s choice to have a child.  If the child lives to be able to go to school, taxpayers must pay for special education for that child.  In ways like this, the choice to have a child that is likely to have a serious disorder imposes costs on society.  Therefore, it would be logical to require testing and to prevent at-risk people from having children.

This is not my opinion, just a possible way to make this argument.