I learned what it is in the hugely entertaining book, Ball Four, by Jim Bouton (1970). He was a baseball pitcher--early in his career, for the New York Yankees. The book was his account of his season in 1969. By then, people could point to the existence of superstars who were of (more recent) African heritage to claim that there was no 'race'-based discrimination in the sport. Bouton pointed out that none of the marginal players were people in that category: to be mediocre (by Big League standards) and be in the Big Leagues a player had to be 'White'. That is where 'White' privilege still makes a difference.