Because lower-class African-American males tend to be obsessed with the concept of masculinity or, rather, constantly proving it: keeping it real, gripping the balls, bashing the gays, partaking in dog fights, take your pick. This obsession arguably stems from centuries of largely manual labour - which has traditionally been the man's - the big strong burly man's - domain. Fragility was, obviously, ill-advised. (hey look: I uncharacteristically ignored the funny!)
hey guise, wait! I'm not racist! I'm just a racial realist!