When Fox News host Laura Ingraham targeted LeBron James in an on-air rant, the conservative commentator pulled pages from a pair of well-worn playbooks.Rappers, boxers and mixed martial artists have long picked fights with better-known rivals to raise their own profiles. Last year, UFC star Conor McGregor trash-talked his way to $30-million (U.S.) payday against pro boxer Floyd Mayweather. Meanwhile, U.S. president Donald Trump has bickered with a litany of African-American sports figures,...