This post is a follow-up to Child Support for Unwanted Children is Wrong.
I am trying to find arguments why it might be morally just to force a genetic father to pay child support, even if he did not wish to conceive a child.
The closest thing to an argument I have come across in support of this proposition is this: What matters is not the rights of the parents, but the best interests of the child. The focus should be on what is best for the child, who after all did not choose to be conceived or born; and it is in the child's interest to have a legal father responsible for her well-being, at least financially.
This argument has some validity; perhaps the focus should be on what is best for the child, and the rights of adults should come second. But we still have no account of why genetic paternity matters.
If we performed a "best interests of the child" analysis when assigning a child a legal father, we would have to look at many things besides genetic paternity. Perhaps the wealthiest candidate should be chosen, or perhaps the one best equipped to be a father. This would very often be someone other than the genetic father of the child.
If consent to sex is all that is required to forcibly assign paternity, why not inquire into which of the mother's former sex partners would be the best father for the child, and assign him the burden? This would be better for the child than always assigning this burden to the genetic father. Better yet, we could force all former sex partners of the mother to share in the financial support of the child, which would certainly be better for the child than having just one (potentially deadbeat) father. But why stop there? Unless we have an account of why consent to sex equals consent to birth, we should really expand the circle of potential fathers to include everyone. (And why limit it to males?) Why should genetic fathers pay child support, and not the public in general or a "father" chosen by the best-interests-of-the-child lottery - regardless of whether he had sex with mom?
In forcibly assigning child support to someone against his will, why does genetic paternity matter at all?