Based on what real world example? Why would an organization subject to ever-changing political whims, staffed by employees with union protected jobs, and whose decisions are subject to every politician's pocket lobbyist be more trustworthy than one that lives and dies by its reputation?
Arthur Andersen messed up and paid the price. The bond-rating agencies were corrupted and are now paying the price. How many government agencies have been shut down due to corruption or incompetence? How many government agencies have increased their budgets and staff DESPITE their track-record of incompetence?
No human-built institution is perfect, public or private, but I'd prefer to put my trust in the one that depends on its reputation over one that depends on politics every time.