"It can't be whites vs blacks, politicians that black people voted for did it too".
When you actually write out your argument it doesn't make any sense. What if they were given two options, both of whom would have continued racist policies? There's also a phenomenon whereby politicians identified with a specific "outsider" group have a lot more pressure (and ability) to defy the interests or stereotypes of that group. H Clinton under a lot more pressure to be hawkish to defy weak women narrative. Obama under a lot more scrutiny about anything that could be seen as a handout to African Americans. Politicians from the left often ripping up regulations, because they sedate the left who would have prevented right candidates from doing it.
Basically, it's way more complicated and your argument doesn't hold water.
https://www.theguardian.com/us-news/2018/jun/05/trump-prison...
[1] https://www.goodreads.com/book/show/680751.The_Marijuana_Con...
[1] https://www.nytimes.com/1982/10/04/obituaries/rev-oberia-dem... [2] https://books.google.com/books?id=Pit7gWBM6M0C&pg=PA31&lpg=P... [3] "The Congressional Black Caucus secured a closed-door sit-down meeting with President Nixon in the Cabinet Room. During the session, the group demands more action to stop the flow of narcotics into urban neighborhoods."
1. http://www.people-press.org/2018/03/20/1-trends-in-party-aff...
2. In a speech at an NAACP convention in Philadelphia in July, Clinton acknowledged that tougher incarceration provisions in the bill were a mistake. “I signed a bill that made the problem worse,” Clinton said. “And I want to admit it.”
I think this issue has many different angles than just the usual whites vs. minorities.