Hit Piece Meaning

(idiomatic) a published article or post aiming to sway the public opinion by presenting the false or biased information in a way that appears objective and truthful

Example: 2013, Eric Dezenhall, ‎John Weber, Damage Control (Revised & Updated): The Essential Lessons of Crisis Management
  "And respectable media institutions do have their standards, but there is something insidious — and very human — at work in the preparation of a hit piece: the media's desire to believe in the evil of their targets."