This is the worst video of black mob violence you will see today. Maybe ever: Four black children beat and taunt a three-year old white girl. Then the cameraman posted it on Facebook over the weekend with the heading, “When white people piss black people off.” The video begins in the middle of a street in Minneapolis. Two black girls, twice as old and twice as big as the white girl, are screaming at the girl on a Hot Wheels tricycle. “Stop spying on us,” shouts one. “You ugly.” Then the violence begins: The two girls each grab one of...