FILE - In this May 10, 1967 file photo, Muhammad Ali, former world heavyweight boxing champion, speaks at an anti-war rally at the University of Chicago in Chicago. Celebrities have long played a significant role in social change, from Harry Belafonte marching for civil rights to Ali‚Äôs anti-war activism. LeBron James and other basketball stars made news in 2014 when they wore t-shirts reading ‚ÄúI can‚Äôt breathe‚Äù to protest the death of Eric Garner. Just last month, ‚ÄúGrey‚Äôs Anatomy‚Äù star Jesse Williams just gave a passionate speech at the BET Awards calling for unity against police brutality. (AP Photo/Charles Harrity, File)