It hasn't.
Yes, but that's not the issue here.
I don't agree with a literal "license" being involved.
You don't think that's a BIG difference? 
Race has nothing to do with one's ability to raise children (that idea was based on the unethical concept of eugenics and "genetic purity" associated with the Aryan ideal looked up to by the Nazis). Culture, however, has a significant impact on how parenting is done, and can shape a person's way of parenting easily as it is passed on from generation to generation. This is not to say that cultural differences should be used against people, but I wanted to make this aspect clear so that my next point is more clear.
Good parenting is a complex issue. It involves a great deal of variables that aren't easily diagrammed out and understood. Therefore, one would expect to need a very thorough and well-researched line of study should be responsible for ascertaining the qualities that best exemplify what a good parent is. This would need to take various things into consideration such as culture, income, living situation, stability, etc.
I would personally prefer that education standards would include classes (or at least mini-courses) on this topic that seriously delve into the topic and ensure the students learn everything they need to know in order to be a better parent; no matter what background they came from.
Of course, this isn't an easy task. It requires more than many teachers are willing to do for their students, and highlights the serious deficiencies of the current standards for teachers' employment.
I know that - that's why it was a joke.
In fact, many people in the US were sterilized as ruled by courts in many southern states (as well as others) in the first part of the 20th century due to the rising interest in eugenics. Thanks to a limited, paltry understanding of genetics at the time, the interest was rather wide-spread for a while. This concept, of course, was what fueled the same ideas in Germany in the coming years; particularly with Hitler, who ran with the idea once he gained power.
To attribute these things to what I'm talking about above is about as ludicrous and inane as it gets.