FACED WITH DECLINING circulation, many U.S. newspapers are trying to engage readers by allowing them to respond to news stories online. But the anonymity of the Internet lets readers post obscenities and racist hate speech that would never be allowed in the printed paper.

Consider one reader comment this month on the Web site of Nashville’s daily newspaper, The Tennessean: Some ethnic groups were told to “go back where you came from” while one was singled out for comparison with insects.