Bottom line: When a cop orders you to do something, do it. If the cop s wrong, you can always complain later to the cop's superiors or to the political officials who oversee the police department. If the cop is really wrong, you might even be able to sue. But you cannot win a testosterone contest with a cop on the street.
Plus, even if you are riding lawfully, the cop may have a good reason for telling you to move over. Maybe emergency vehicles are coming. Maybe a funeral procession. Maybe something else.
Comply first, complain later.