The dirty little secret that's never mentioned as a possibility for the lack of blacks is that history has shown that they just aren't very good at baseball. In the over 60 years since Saint Jackie Robinson broke the color barrier, blacks enjoyed one relatively brief era of success in the sport at the professional level, from the mid 1960s through the early 1970s. Before then and ever since then it's been a much different story. That era was marked by numerous great power hitters and a few top pitchers.
Ernie Banks, Willie Mays, Hank Aaron, Roberto Clemente and even Willie McCovey were relatively slender, strong but lean more than burly. Willie Stargell was more in the burly category but looked nothing like fat boys Fielder, Ortiz, and Sabathia. SinceStargell most black power hitters have been obese types who have to walk through doors sideways and who quickly decline as sumos are just not cut out to be home run hitters for the long term. The ones that did last, such as Bonds and Sosa, were obviously chemically enhanced. Ken Griffey Jr. may have been a rare exception. Dave Parker started off in shape but then after receiving his first big contract, overnight became a fat piggy who instantly declined dramatically from his former greatness.
Other than Bob Gibson and Ferguson Jenkins, there were virtually no star black pitchers during those glory days that blacks (and their weeping supporting army of emasculated and deracinated whites)constantly pine for. Vida Blue had a few good years but no durability. After 60 years of integration, the truth is that blacks are not better baseball players than whites and their 8 percent representation is fair, especially given the concentrated efforts MLB makes to recruit and draft them and to build academies specifically for them (and also for hispanics; only whites are denied such opportunities). If blacks are such wonderful athletes, just those who barely miss out on the NFL and NBA should be able with ease to make it in Major League Baseball -- not. It takes a skill set, especially excellent hand-eye coordination, to succed in baseball; blacks are known for poor hand-eye coordination on average. A good black American pitcher, where hand-eye coordination is paramount,is almost as rare as a good black hockey player.
It's a different story in batting, but other than the rare Tony Gwynn, hitting is dominated by whites and hispanics. Yeah there's Ryan Howard and his crappy batting average and 200 strikeouts, and superfat Prince Fielder, and obese David Ortiz, but none of them will have the durability to challenge any records unless they have the willpower to lose weight and prolong their career without noticeably affecting their power. So many talented "professional" black athletes seem more concerned with eating to their heart's content than being a finely tuned beast on the field of play.