In the streets of his native Harlem, Joseph Hayden is a familiar presence, patrolling the neighborhood with his video camera, ready to document interactions between the police and the residents they stop — and doing so at an age when most people have retired. “Like I tell them,” Mr. Hayden, 71, said recently of the police, “I’m on your side to make sure there is courtesy, professionalism and respect. Isn’t that what you advertise on the side of your car?” “Seems like you’d want me to do it,” he added, “unless what you’re providing is not courtesy, professionalism and respect.”