In 2002 and 2003, Yun became an activist for human rights and peace. In March 2003, he was a conscientious objector to South Korea's conscription military service. But his opinions did not matter to some Koreans, because of his sexuality. In early April 2003, some South Korean Christian organisations gave a statement against homosexuality. Yun spoke out against this and wrote an article to some South Korean newspapers and the foreign press.