An anti-gang initiative being launched Tuesday in Wyandanch would initially target 37 admitted gang members and keep them from intimidating people, flashing gang signs or even standing and talking on a 2-mile stretch of Straight Path running through the heart of town...Amol Sinha, director of the Suffolk chapter of the American Civil Liberties Union, said the county could seek to ban gang members from intimidating people or engaging in threatening behavior, but has no right to stop anyone from simply being on a public street. "No government can ban people from gathering on public grounds," he said. "Whether they are gang members or not, sidewalks have been used as public forums from time immemorial . . . you're diminishing an individual's right to freedom of association."