on the meaning of the word 'is'

from Michael Kinsley's Slate

"The Bush argument blaming the CIA for failing to remove this falsehood from the president's speech is based on the logic of "stop me before I lie again." Bush spoke the words, his staff wrote them, those involved carefully overlooked reasons for skepticism. It would have been nice if the CIA had caught this falsehood, but its failure to do so hardly exonerates others. Furthermore, the CIA is part of the executive branch, as is the White House staff. If the president—especially this president—can disown anything he says that he didn't actually find out or think up and write down all by himself, he is more or less beyond criticism. Which seems to be the idea here."