Just say you are unarmed but somehow you find yourself in a scenario where a bad cop is doing something illegal and potentially dangerous to you or someone else and there is no one around to help. Such as you come across an officer assulting someone late at night in a desolate stretch of road and just beating them senseless beyond any reasonable need to control that person and when you try to stop him he comes after you. Would you put your fists up or just walk by like you didn't see anything?