Scientists have been working around the clock for decades to conquer AIDS, a tragic disease spread by a deadly virus that has already killed tens of millions of people. Like most crises, AIDS has brought out the best and the worst in human nature. Thousands of professional and voluntary care-givers have generously come forth to care for the sick. . . But AIDS has also aroused mean-spirited responses due to the fact that the disease first struck already stigmatized populations: gay men, IV drug users and prostitutes.