A leading American AIDS group said it was suing Pfizer, the producer of Viagra, accusing the company of increasing the spread of sexually-transmitted diseases through "irresponsible" marketing. AIDS Healthcare Foundation, the largest AIDS healthcare, prevention and education provider in the United States, accused Pfizer of deliberately pitching the erectile-dysfunction drug at men who did not need it. "Pfizer's direct to consumer marketing of Viagra as a drug to enhance sexual performance is primarily aimed at men who don't necessarily suffer from a clinical diagnosis of erectile dysfunction," the group's president, Michael Weinstein, said in a statement. "We believe it is...