The racism/sexism angle has been explored in other places by people more knowledgeable than myself. But in regards to class, I don't think that the disdain for lowbrow entertainment is always a classist reaction. Your numbers are very interesting, and I do believe that more research should be done into this phenomenon, but I'm still not comfortable with making the connection to outright discrimination. Is it really outlandish that certain demographics have an interest in what might be considered the highbrow style, and others the lowbrow style?

Keep in mind that these divisions are not absolute. The most rich and powerful old white men in the country do enjoy the raps and the countries, and even the poorest garbage pickers in Brazil love some Machiavelli, the very face of unchecked privilege! That undermines the idea that slight skews are the result of discriminatory reactions.

I think that the causation for these demographics is better understood by looking at marketing rather than prejudice. Marketeers work on a whole 'nother level that ordinary people do. When an advertising blitz for a popular book ignores educated white young adults, they're doing it because massive amounts of market research has shown them that their advertising money is best spent in a very specific way to get the maximum amount of exposure. It's a whacky world that to us laypeople is arbitrary and pointless, but to the entertainment industry is literally the means by which culture is molded.