I have one black girlfriend who's bdsm "parents" made her go to a recent (or she is going) conference hosted by the african american bdsm society or some such name. She was a little freaked out by the idea, wondering what they might think of her and her white playmates.
I am from a majority black city and have only met a few black folks who seems serious about bdsm. Then again, I try not to get out much.
Porn is definately aimed at males, though can be easily enjoyed by females that are openminded as well, my opinion. Why do I say it is aimed at men? Because they usually don't focus much on the men, just the women and the man dick or hand or whatever....not often their faces... Why is this? Dunno, maybe most of the producers and pornographers are straight men or bi women???
There is also, still being fueled and still so on fire, the backlash of the real slavery that existed in the South, I am from the South, and even I a white woman have a hard time taking the term slavery seriously if it is a choice.
Black people down here know what it is like to be submissive and beat down, perhaps if you get it on that level, in everyday life, you don't want to take it to bed...
It seems you could find the truly sadistic or dom types easier according to profession, i hear alot of cops are into it, and i imagine there are other professions that bespeak other kinks...
Interesting question.