Because they probably didn't need to. They had massive amounts of racial violence to oppress minorities, random attacks, lynchings, police raids etcetera.I'm not talking about the racism. Why was there no restrictive crime bill passed in 1940 when the racism was even worse? There's plenty of ways for racists to go after black folks without needing to pass a wide ranging crime bill that also meant white people went to jail for dumb reasons as well.
Later when those options weren't as politically feasible anymore they had to move to more subtler forms of discriminations.