One of the tips says, do not go out at night. Hey where are you from. All larger cities have its problems, sure there are places where you do not go out at night. A European New York does not go cycling through Harlem at night time, in Cotonou you do not take a motor taxi at night time and on the same note you avoid certain areas of the city such as the road in front of the port.
Cotonou is safe if you take care of yourself!