It's a great film, but it's not about no having police. Just the opposite: the country had become a police state, hence the highjacking of AF1. Manhattan was a prison like Devil's Island totally surrounded by police. In an ideal society there would be no need for police. Maybe someday 100 years from now we'll achieve that. Until then we've got to do as much reform as possible and not let criminals join the force.
Defunding local police will lead to a national police force as in the movie. It will be an army trained to shoot American citizens. Be afraid. be very afraid.