It all boils down to very simple psychology;
First you brain wash the people [wash their brain clean] then you have a "Blank Slate" to indocrinate their brain with whatever it is that you want them to believe, think, fear, love, hate, desire, or be indifferent to, creating a "Self-Fulfilling Prophecy" effect that insures the indoctrination(s) will be carried out by those people.
Africans were brainwashed on the cotton plantations of the south and where ever they were held as slaves in the West, they were then told what to believe, think, fear, love, hate, desire or be indifferent to, which created the 'self-fulfilling prophecy effect of whatever the racist propaganda said [and still says] about Black people, people of African descent, it will manifest itself, i.e., if you tell someone something enough times or long enough, they will begin to believe it, and not only that, they will begin to act it out [self-fulfilling prophecy]. So, what have Black people been told since slavery? What have our young people been told? What are many Black people now 'acting out'? What is it that so many of our young people are now 'acting out'?