Defector activist Park Sang-hak on Thursday submitted a letter renouncing government protection from North Korean death threats, accusing South Korean police of using it as a pretext for surveilling him.In a letter addressed to local and national police, as well as the National Intelligence Service (NIS), Park -- whose routine launches of anti-regime leaflets into the North sparked a major escalation of inter-Korean tensions last month -- said he no longer wanted the police protection provided to him for the past 12 years.That protection, he said, had been meant to protect him from "North Korea's murder [and] terror threats