The FBI and CIA....the lakes of Pontchartrain (with apologies to Andy Irvine and Paul Brady)

 The FBI will sometimes put you up in their own home. As policemen,they have no fear of other policemen and are anxious to gain information from the wayfarer to catch a bigger crook such as a murderer.

A CIA man never,unless he intends to murder you,poison you or otherwise  incapacitate you. He is by nature a murderer and as a murderer he is in constant fear of arrest. He doesn't want to further incriminate himself by having 'deleterious material' i.e. incriminating evidence or another murderer in his house who may live to incriminate him.