Bad apples

I remember being mystified back when President Bush defended his administrations stewardship of the Iraqi penal system by saying that the torture enhanced interrogation torture (I guess it was officially, since people got prosecuted for it) at Abu Ghraib was the work of “a few bad apples”. I guess that phrase had been going around for a while, and now it’s certainly common. (For example, here is the assertion that “a few bad apples” are responsible for most complaints about doctors.)

But back in 2003 I was confused by this expression. Bush seemed to be using it to mean that the US occupation of Iraq, and the US military and antiterror policies more generally, were sound, and that the crimes were the isolated work of individuals with no broader implications. But why apples? Why not “a few bad people”? The reference is clearly to the phrase “one rotten apple spoils the barrel”. But that expression has exactly the opposite implication: Rottenness is not isolated. If you’ve found “a few bad apples”, you must expect that the rot is widespread. Now, there’s nothing compulsory about that metaphor — you may not think that one bad individual casts suspicion on the rest — but why are apples being gratuitously referred to when the desired implication is exactly the opposite? How did this adage get turned into its converse? Or is the referent actually something else?