Over half of black men have dated a white woman according to a Gallup poll.
JBB theory stands for Just Be Black theory, and stands for believing the being a black is the best way to attract white women because white women get off on big men, big cocks, and traditionally taboo behavior.
Big Black Cock Theory is a subset of JBB theory that states that JBB is mostly due to the size of black penis and not historical taboos or the black man's personality.
Reasoning for usage
The term was coined and used primarily in the incelosphere for whitecels to scapegoat their own sexual failures onto something.
The term is now primarily used on Reddit to describe a type of Black-male-white-female pornography. Most notably /r/JustBBlack.