The Mann Act was designed to stop prostitution. There was no evidence Johnson was engaged in prostitution. His crime apparently was being a successful black boxer.
No his "crime" was being a black man who had the audacity to consider himself to be equal to the whites.
And a good point is made concerning why Obama didn't address this pardon? There is probably an explanation. Just have no idea what it is.
Volvo
“Build a man a fire, and he'll be warm for a day. Set a man on fire, and he'll be warm for the rest of his life.”