President Barack Obama expressed sympathy for the family of Trayvon Martin, the unarmed 17-year-old who was shot dead by neighborhood watch captain George Zimmerman in Sanford, Florida on February 26. "If I had a son," the president said, "he'd look like Trayvon." Some Republican presidential candidates seized on those comments, calling them divisive. But Don Lemon asks, who's really politicizing this tragedy?