Despite the admirable cloaking of all this in the garment of "the American public", the White House press corp's anger is based on one thing: Scott McClellan lied to the Whitte House press corps. The President, the Vice President, the Army and Navy football teams, the Secretary of State--all of them can lie to any or all of the planets in the solar system, and hey, that's politics. But, stand
at that podium, and lie to those people, and let them eventually find out about it, and, brother, you got trouble.
There is a lot of truth to this. Clinton's famous "I did not have sex with that woman..." caused them to screech about lying to the "American public" for months, but what upset them was that it was actually wasn't a statement to the cameras (though the cameras were on), it was a statement to the press corps. That was what drove them insane.