EARVIN "MAGIC" JOHNSON wanted to return to the National Basketball Association as a player three years ago. He couldn't. It wasn't that his having the virus that causes AIDS had made him physically unable to play. But it was obvious that if he played, many of his opponents would not. They would be in constant fear that any accidental scratch that caused Mr. Johnson to bleed would put their own lives in danger. It didn't matter that medical experts said the possibility was remote. That's what they thought and they let Magic know it. Five weeks after announcing he was ending his retirement from the game, he announced he would stay retired. That was 1992. Tuesday night, Magic Johnson was back on the court for the Los Angeles Lakers, the team he led to five NBA championships in 12 seasons. The whispering and the loud protests that caused him to postpone this moment three years ago have not been heard this time, at least not yet. That Mr. Johnson has been welcomed back into professional basketball says a lot about how much this nation has come to accept HIV as a part of life. We still fear it, but we know it shouldn't be dangerous to work or play with someone who has the virus. Our maturity has come at a high cost. More than 500,000 AIDS cases have been reported since 1981. More than 13,000 have been in Maryland, half in Baltimore. Currently there are between 750,000 and 1.2 million Americans with AIDS or HIV. We know more about the disease now than in 1991 -- when Magic Johnson told the world he was HIV-positive -- because so many of us have known someone with the disease. Familiarity with HIV is helping to erase discrimination against its victims even as scientists progress toward containment or cure.