Social media has become unsocial, chockful of fake news, extremism and sexism, and one of the world's biggest advertisers has had enough of it. Unilever is threatening to pull its advertising from digital platforms that it says have become a “swamp.” Keith Weed, head of marketing at Unilever is expected to deliver a forceful warning to digital platforms such as Google during an advertising conference in California later today.  “We cannot continue to prop up a di...