Jack Johnson was one of the first great American boxers. He was certainly the first great black American boxer. In death, he has become a cause célèbre for the glitterati and politicians alike, his story gracing the silver screen and the small screen, and his vindication has been taken up by John McCain, among others. Maybe it shouldn't be.The movement is strong and noble in its surface intent, getting Johnson pardoned for a supposedly racism-tinged 1913 conviction for viola...