Feds are the most detached from people so they can treat people as numbers than individuals. The lower you go from state to officer Bob at a local station, the more connected they are to their communities so less likely to do horrific things.

There's an easier way to show this in history with Machiavelli as he recruited people for a local militia than rely on mercenaries like other city states as a militia would fight till the end as their families live there, mercenaries would switch sides at the chance of losing. Same applies to Feds and local police.