HEALING demands compassion. And one problem surrounding the AIDS epidemic has been a lack of compassion in the mainstream of society for victims of the disease. The people afflicted with AIDS were too easily categorized as a separate segment of the population, distant from the heterosexual, non-drug-using majority.That has long been an oversimplification. But Magic Johnson's dramatic announcement that he's infected with the AIDS virus should help put that perception to rest for good. Here is a man who has personified many sound values - he's hard working and likable. While he, like many other NBA stars, may have succumbed to the fast life of the pro basketball tour, the Laker star set a standard for decency on the court and in his treatment of his fans. Would he be someone to shun and isolate because he has been touched by this disease - the way victims ranging from homeless junkies to innocent schoolchildren have been shunned? AIDS has generated fear, even hysteria, along with its suffering - fear that has kept people from getting the compassionate care they need. Johnson's first impulse on learning of his infection was to commit himself to helping others protect themselves. "Safe sex" is the byword of AIDS prevention. It's a reasonable, practical path for many - a step toward greater responsibility for oneself and others. The message needs to be reinforced, and Johnson's words should help. The message of abstinence before marriage and rejection of promiscuity must also be reinforced. AIDS presents society with multiple challenges - social, medical, ethical. Each individual can take a step toward meeting those challenges by finding the compassion to recognize the worth of others regardless of their affliction.