Dusty has a point to an extent...
Baseball is different than other sports.
In basketball; if the ball goes through the hoop, nobody decides, "nope, not 2 points". If the ball crosses the goal line in football; nobody says "nope, not a touch down". If the ball goes into the back of the net in soccer, nobody says "nope, not a goal". Baseball is one place where jaded umpiring can really affect a player's performance. Maddux, Glavine, and Smoltz famously (or infamously) got an inch on either side of the plate. Did Dontrelle Willis get the same consideration? Maybe, maybe not. Did Craig Biggio get balls called that were borderline because he was white that Tony Gwynn didn't get? Maybe, maybe not.
That being said, what Baseball also has that other sports don't have is the constant one-on-one match up; pitcher against hitter. Vlad Guerrero would hit anything in the vicinity of the plate. That part is all desire. You have to have a coach that is not going to "coach it out of you" too. Eric Davis--a good power hitter for the Reds had a hitch in his swing. It didn't matter when he was cranking close to and over 30 homers in a year while stealing as many as 50 bases once he got on.
I think the major problems are that you have to have 17 other guys who want to play ball, umpires, 18 gloves (counting catchers mits), bats, balls, a very large patch of green grass.... Soccer and basketball are much easier to just get out there and play. These are likely much larger obstacles than jaded/racist umps.
Of course, the place where jaded and racist umps can really effect a baseball player's life is on the pitcher's mound.
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Not a lot of diversity there.