For the former, I'd recommend chapter three of Thomas Sowell's Black Rednecks & White Liberals, about the history of slavery.[1]
For the latter, I'd recommend Illiberal Reformers, about the Progressive Era and its devotees.[2] Later Progressives were responsible for the school-to-prison pipeline and militarized police.[3] The Progressive Era has a wide array of interesting literature, including the writings of many of its early exponents (since they tended to be writers or academics).
[1]https://www.amazon.com/Black-Rednecks-Liberals-Thomas-Sowell...
[2] https://www.amazon.com/Illiberal-Reformers-Eugenics-Economic...
I voted for Obama. However, in retrospect, he was part of the shift of the American left into an authoritarian version. Those collegiate "progressive" protesters who say, "F your free speech" are part of this unfortunate shift.
which toxic culture are they supposedly glorifying?
Urban thug culture.
https://www.amazon.com/Black-Rednecks-Liberals-Thomas-Sowell...
There is a genteel African American culture. I've known people from that thread of American culture. It valued learning, rationality, responsibility, and manners. Also, not all Black Americans are too crazy about Obama's legacy.
https://www.youtube.com/watch?v=phPXTWJhnYM
https://www.amazon.com/Quest-Cosmic-Justice-Thomas-Sowell/dp...
https://www.amazon.com/Discrimination-Disparities-Thomas-Sow...
https://www.amazon.com/Black-Rednecks-Liberals-Thomas-Sowell...
https://www.amazon.com/Wealth-Poverty-Politics-Thomas-Sowell...
The very idea that, in a just world, outcomes along various lines of demarcation between groups of humans would be roughly even has zero evidence to support it. In fact, all of history, as well as the state of the universe itself, testify that this should not be the case! Never has there ever been equal outcomes between any groups in history. The world is complex, and the causes for disparity are too numerous to list and impossible to even attempt to measure or tease apart in their impacts. Sowell has written about numerous causes of disparity between groups that have nothing to do with racism or any societal injustice, and the above book examples are just a small portion of what he has written.
What leftists like to do is over-simplify the world to fit their pre-conceived notions. If there is racial disparity, it must have been caused by systemic racism! Therefore, we must fix it through systemic racism in the opposite direction! This kind of thinking is broken, flawed, and completely incorrect to the core, and acting on it simply leads to more injustice, more unfairness, and more disparity of different kinds. It is an ideology born of intellectual pride, moral vanity, and an utter lack of wisdom.