Black athletes showboat too much.
Part of streetball culture that many black athletes grow up in, involves showing up your opponents and shit-talking them relentlessly. It's a culture of pounding your chest, declaring your greatness, and getting in your enemy's face. Sport traditionalists may think of this as poor sportsmanship, but to us, it's entertainment.
It's not only black athletes who love to gloat on the field—all athletes with a nasty edge and some hubris do too. While this stereotype may extend itself from a black cultural attitude, it's branched out to all races today. Remember Marshall Henderson and how about soccer players celebrate after scoring goals? If you want to take way back, how about Babe Ruth's called shot?