Last week, Daniel Vasella, chief executive of Novartis, the Swiss pharmaceuticals company, hit back at animal rights activists who have attacked both him and his company, including the desecration of a family grave. This fightback has been an unusually aggressive public response by a CEO. Many prefer to keep their heads down and wait for protests to fade. How should business leaders engage with hostile critics: confront them, bring them inside for a talk or ignore them?