A lazy Wiki snip:
Violent crime nearly quadrupled between 1960 and its peak in 1991. Property crime more than doubled over the same period. Since the 1990s, however, crime in the United States has declined steeply.
I'm sure there was probably always some racial influences, e.g. perhaps people were more willing to hand out harsh sentences because the defendants were mostly black. But to say that "Tough On Crime" was really just a cover to marginalize african americans & nothing more... it just seems like a stretch when you suggest everyone was in on it.