I agree. BBC is a myth that exoticizes the black body, it's racist, really. The reality is more social: black men are statistically poorer, they're more likely to be sex workers (minorities in general are, women, black women, trans women, black trans women...) be it in prostitution or porn. Society has animalized the black body for centuries - it started in the XVI centuries with the first accounts of African Tribes. Science has proved that skin colour and penis size are unrelated.
My penis is big, I've called horsehung, huge etc... but my social class has always prevented me from doing porn - that would be frowned upon, I would be "déclassé". Porn actors, most of them, come from the working class or even lower social statuses (unemployment, dole/warefare, addictions, gangs etc). Danny D has a huge white cock; he's also a bit of a chav. Had he studied in Oxbridge, he would have become a hung posh dude like me. His cock would have remained more of a "secret". I was lucky enough to be brought up in a rather affluent environment. If I had been poor, I might have considered porn to make ends meet.
Well hung black dudes have found a way to make easy money. Their size is also sometimes exaggerated. Mandigo looks huge but he's very short and his balls are small. He's very big though (a real 9incher, at least). I must confest I never found Lex Steele "huge". I think he's 8-8.5x 6-6.3. Of course that's big and rare. But there are as many white dudes with similar cocks. My own cock is in that league, ballpark.
They also all pump, use injections, sometimes surgery, and angles are flattering.
So to sum up, there are as many big black cocks as there are big white cocks. But black bodies are animalized, praised under a false pretense, in order to be denigrated and segregated, at the end of the day.