The 9 Principles of Libertarian Eugenics

1. Women who do not find a husband before getting married will be treated as lower in status compared to women who are married when they have children.
2. No parent may be prosecuted for infanticide if the victim is their offspring.   
3. Home births will be the rule rather than the exception.   
4. Feminism (because it condones the poor reproductive choices of women and makes them beyond criticism) is anti-eugenic, immoral and must be destroyed.   http://thebattlefieldoflove.blogspot.com/2012/01/how-to-destroy-feminism-in-6-easy-steps.html
5. Eugenics, if practised by individuals only and not by the state, is moral and must be practised.
6. No person may be married without a legally enforceable Marriage Contract.  
7. No person may be divorced without fault being attributed and/or damages quantified and paid  to the wronged party.
8. Same-sex couples may not "marry" or "civilly partner" each other.   
9. All drugs will be legalised so that the weak-willed, depraved and stupid who succumb to addiction will perish sooner rather than later.  

http://en.wikipedia.org/wiki/Eugenics

Eugenics is the practice of improving the genetic composition of the population.  

Marriage is therefore Eugenic because requiring a woman to find a husband before she has children will make her choose a long-term sex partner more carefully and wisely.

If she were rational, she would choose a male partner with good  prospects who seems to her to have the potential to be good husband and father (thus improving the quality and increasing the numbers of men who wish to have good quality offspring with the best kind of women, because most men will do anything for sex).

Not requiring a woman to be married before she has children makes her careless, selfish, unwise and promiscuous.

Tolerating the existence of never-married mothers and suffering their numbers to increase without taking strong radical action to discourage them will eventually lead to a populace with the morals of a sexually incontinent, irrational and tyrannical woman leading, eventually, to the decline and fall of your civilisation.  

If Marriage (which is considered sacred by those who believe in God or at the very least necessary to ensure a cohesive and civilised society) is Eugenic, then the practice of Eugenics as outlined above is inescapably and undeniably moral, because the practice of it is necessary to the social cohesion of your nation if it is to continue to exist and flourish.