EARLIER THIS month, amid relatively little media fanfare, the National Organization for Women celebrated its 40th anniversary. [...] NOW's 1966 statement of purpose declared: ``The purpose of NOW is to take action to bring women into full participation in the mainstream of American society now, exercising all the privileges and responsibilities thereof. . . . [...] While paying lip service to the idea of equal parenting, NOW has steadfastly opposed efforts to broaden the rights of divorced fathers. With the exception of a few chapters, it has staunchly opposed such proposals as joint custody and mediation instead of litigation. Ten...