Gaddafi, Hussein, Hitler, Mussolini. Each of these men believed they were right to the detriment of many. They were, however, overthrown to the salvation of many. Nineveh could rightly be included in this list - thinking they were living right while God described them as wicked. Frankly speaking, we could be included in the list.
Jonah 3 records the message of God and the immediate response of the people of Nineveh. How should we respond? When should we respond? What are the expected results?