MIAMI — Author and folklorist Stetson Kennedy, who infiltrated the Ku Klux Klan six decades ago and exposed its secrets to authorities and the public but was also criticized for possibly exaggerating his exploits, died Saturday. He was 94. Kennedy died at Baptist Medical Center South near St. Augustine, where he had been receiving hospice care. In the 1940s, Kennedy used the “Superman” radio show to expose and ridicule the Klan’s rituals.