You know how bitter the longstanding dispute between Tamil Nadu and Karnataka over the sharing of the Cauvery waters has become when movie stars of the two states wade into it. For instance, when Karnataka objected in 2008 to a drinking water project Tamil Nadu was planning in a town close to the border the states share, Tamil actors went on a protest and Rajinikanth, a Maharashtrian who grew up in Bangalore, wondered aloud: “If Karnataka objects to us taking the water that is rightfully ours, should we not teach them a lesson?” The poser invited threats from Karnataka that his films would be banned there.