Any person found loitering or standing on any street, sidewalk, curb or in any public park or building shall move on when required to do so by a police officer of the city who must have a reasonable suspicion that such person has no lawful purpose and may be a threat to the public health, safety, welfare, morals or convenience. Any such person who fails to move on or who commences to loiter in another such place shall be deemed guilty of a simple misdemeanor.