Yes one adult can control a nine year old girl, but the police have restrictions in place that disable many of the methods adults can implement to control the child.
Everything the police do is recorded and analysed after the fact, any slight miscalculation in the heat of the moment and it will be headlines. Every person they come into contact will act and react differently and they have milliseconds to process just about every law to conform to standards. Its a job not many last long at because of the stress involved.
Smart people like you me and stewie would never be policemen because we know the how the public treat police. People are free to abuse the police and there is no support from the public, its a lonely life being a police officer, nobody trusts or likes you. As I said most leave the force because the stigma of being a police officer impacts on you and your family.
I see a larger more sinister quantity of disrespect for the police from the general public than I see the police disrespect the public.