How come when a black person commits a crime, people always make racist comments?

If a black person commits a crime that is seen as a "black crime", usually something violence like beating someone up, or shooting someone, people always seem to make an load of racist comments. But when a white person commits a crime that seems to be steryotypically "white" like child molestation, people only refer to the indivual as a monster, but no one seems to say anything about the race. Theres no jokes about how people arent surprised that a "cracker did it"