If the destruction of Black America came from the stroke of anyone's pen it was Lyndon Johnson (D) with his massive welfare state. His comment regarding his "Great Society" initiative was "We will have those (N word) voting democrat for 100 years".
From then on, every statistic you can point to was downhill for ''Black America". Employment rates vs whites, two parent families, crime rates ,life expectancy all got worse as generational welfare and particularly single mother households became common and acceptable.
The only good piece of legislation regarding minorities was the Civil Rights act of 1964 that was pushed through because of republican support over democrat objections. Including northern democrats. In truth, the democrat party has been on the wrong side of every major race conflict dating back to pre-Civil War days.
To the extent that the modern democrat party "cares" about African Americans; it is patronizing and insulting to them as if they still can't do it without help.