Why Protect A Lying Source?

Were the Washington Post and Newsweek used to "Swiftboat" Governor Blanco? Now that the word is out that the Washington Post and Newsweek were falsely told by a "senior Bush official" that Governor Blanco of Louisiana did not declare a state of emergency, the next logical question is whether a news organization is obligated to "protect" a source who knowingly and intentionally lied for political purposes. If the Washington Post and Newsweek do not immediately identify the source of the lie, then they are part of the propaganda machinery.