I'm pretty sure it has to do with reversing some of the negative imagery society has given to the profile, the stereotype, the generalization of "black people." People (and now I'm grouping, too) sometimes think that, to secure their safety, they need to make rash judgments: threat or no threat, fight of flight. At the end of the day, they think black people are scary because they're more black people in jail than anyone else.
Racism has more to do with that figure, I suspect. It's has to do with constructivism and the endless cycle of definition and connotation. You see, police officers are human beings too, and with that flaw they also stereotype. They're more likely to arrest a black man than any other person.
I'm not black (if you couldn't tell by my profile image) but I strongly support the sentiment of "I am black and proud." God made you this way, most likely (in my humble opinion), because you (as group) are stronger than the rest of us—more resilient to senseless bigotry and the age-old epidemic of In-Out Group Mentality.
I hope this helps :)