Now the middle class world of mumsnet may not like it, but these police will deal with scum, day in day out throughout their careers. Thieves, rapists, child abusers, murders, wife beaters.
As is increasingly becoming clear, quite a few police are themselves violent thugs, rapists and abusers. You don't need to be a 'middle class Mumsnetter' to understand that, or to know that dealing with scum doesn't mean you should be sinking to their level.