The notion is repugnant and sick, and it serves to illustrate why libertarians will never be taken seriously by decent and morally aware men and women.
It does not matter what you or I think about this issue. The Constitution was written is rather simple English and established the powers of the Federal government.
If you can site the exact paragraph in the Constitution that granted the Federal government the power to make laws pertaining to a specific family, we are all ears!
If not, then the laws of our land have been obeyed correctly on this issue.