Trying to retrofit modern post-Industrial concepts of "race" to a pre-modern people or text is not going to work out. Simply because the very notion of "race" that we have today didn't exist until rather recently in the history of civilization.
People then understood that there were tribes or nations of people, but a bronze age Levantine people would have had no notion of "black" and "white" as these are used today. Certain people were lighter and darker, and that was known sure; and different tribes and nations of men shared different characteristics, cultural, linguistic, physiological; but that is a far cry from the language and ideas that we typically employ today which is rooted in a particular recent history and unfortunately flavored often by various pseudosciences of the 19th century (such as the "five race" theory).
But the Bible doesn't know this, because it couldn't know this; no more than it could know about Mexico or the Magna Carta.
Instead the story serves to describe a tribal genealogy, a mythological telling of the foundation of nations which Israel understood. Shem is clearly the important son of Noah, not because he founded a "purer race" or some nonsense, but because through Shem comes Abraham, the patriarch, who is given the promise of child and nation, to whom is born Isaac, and to Isaac is born Jacob, renamed Israel, and his twelve sons the patriarchs of the twelve tribes of Israel.
Shem's importance is found in the fact that he is the genealogical father of Israel in the entire Noahidic episode. And Genesis is, more than anything else, the story of beginnings; specifically Israel's national beginnings. Serving as a prologue to the Exodus and the establishment of the national covenant at Sinai.
-CryptoLutheran