How do I say no to the police?
Just say no.
If you can say no to an insurance salesman who is trying to sell you insurance, you can say no to a cop: he is trying to sell you a prison term.
The police are an instrument of the State, not your mother or your priest.
The street is not the place to object to police actions, assert your rights, and seek fairness or justice. That is what goes on in a court.
Just say no and call your lawyer from jail.
Loose lips sink ships.