Is it a public relations charade or a sincere attempt to root out some bad actors?Motors Corp. hires former Labor Secretary Lynn Martin to investigate charges of sexual harassment at its Normal, IL, assembly plant. "I will have complete independence," Ms. Martin says. Responds Patricia Benassi, attorney for the 29 Mitsubishi employees who brought the complaint before the Equal Employment opportunity Commission: "I don't see this as any kind of major development. Martin isn't a trained investigator. She's a politician" In a hint that Mitsubishi is dropping the stonewall strategy, Tsuneo Ohinouye, chairman of Mitsubishi Motor Mfg. of America, says, "We acknowledge some cases (of sexual harassment) have happened, but not on the scale that was publicized." As if Mitsubishi doesn't have enough problems, the Rev. Jesse Jackson and his Rainbow Coalition targets Mitsubishi for a boycott until it does more business with minority car dealers and suppliers. Mitsubishi says 43 of its 500 dealers are minorities, 22 of them women.