The iconic image of John Carlos at the 1968 Olympics in Mexico City—shoes off, head down, black-gloved fist raised in salute—has come to define the spirit of protest that infused the late 1960s. This spring, as the New York Public Library remembers the 1960s in its exhibit, You Say You Want a Revolution, Dr. Carlos speaks with sports writer Dave Zirin about the principles behind the protests of athletes, and what power they have to impact culture and influence politics.