When the Legislature last year backed the nation's first ban on gay conversion therapy for minors, lawmakers had in mind the experiences of people such as James Guay. At 16, Guay's devout Southern California Christian family placed him in therapy in an attempt to put a stop to his same-sex desires. Decades later, he calls the therapy "quackery" and psychological abuse -- and is among many gays and lesbians now defending the new state law in court. "Parents can teach their children whatever they want," said Guay, now 41, a pastor's son who lived 20 years in San Francisco until moving recently to West Hollywood. "What they don't have a right to is knowingly or unknowingly using the guise of psychotherapy to damage their children."