INDEPENDENCE, MO— The murder trial of three Symbionese Liberation Army members is providing Americans with a nostalgic escape to a carefree, more innocent time. "Oh, man, Patty Hearst and the SLA. That takes me back to high school," said Ralph Henderson, 43, an Independence-area dentist. "Pet rocks, Jerry Ford jokes, small bands of kooky, disorganized terrorists shooting up local banks... Those were the days."