Because it's not meant to be pornographic which is the way Shapiro wants to interpret it and how it shows a decay of western values. It's just meant to be a silly song and he's taking it so seriously to the point it becomes ridiculous.Nah... there's an equivalent of that kind of stuff for white people or people of any race (e.x. Insane Clown Posse for white trash, I guess).
Beyond that - why anyone would listen to a song about "Wet Pussy" when they can just jerk it to actual free porn instead is beyond me. (Most likely the only reason that songs like that exist is because they're able to not trip over the fine line and become actual porn or obscenity, and therefore are able to crack into the radio and digital download market, rather than be confined to a porn site).