The editorial "Family Tragedy," June 21, while deploring the "alternative lifestyle" of single female parenthood, says nothing of how our society, through films and the media, teaches our young men to expect to have sexual freedom without affection for their partner or responsibility for the consequences of their actions. What is needed is a re-stressing of the masculine maturity that is compatible with fatherhood: responsibility, caring, and cooperation in a society that encourages the opposite.If the highest birthrate increase for unmarried women is among mature women in their 20s, it may be because the "men" they date are too immature to be a father and husband. It is not merely the "expendable father," or the idea of the super-feminist rejection of the male, but that some of us feel a family without a husband is better than a family with an abusive or immature husband, or forgoing motherhood. Unfortunately, our sons may never see the "positive" role models that they need to become caring an d loving men. Nancy O'Connor, Nanty Glo, Pa. Letters are welcome. Only a selection can be published, subject to condensation, and none acknowledged. Please address them to "Readers Write," One Norway St., Boston, MA 02115.