forged documents, combined with shoddy reporting, have been used to debunk what is actually a true story
You thought he was talking about the Bush-National Guard story? No, he's talking about the Niger-uranium story, which he insists still has legs.
McCarthy links to this piece from Christopher Hitchens, in which Hitchens argues, in so many words, that Iraq must have been trying to obtain uranium from Niger, because what else could Iraq's ambassador to the Vatican been doing in Niger other than trying to obtain uranium?
Back in 2003, Wissam al Zahawie responded to the assertions in Bush's speech, claiming that he was in Niger as part of "an unsuccessful tour to persuade African leaders to break the UN embargo and visit Iraq." He also visited Benin, Burkina-Faso and Congo-Brazzaville (and what else could he have been doing there except trying to acquire sharks with frikkin lasers attached to their heads?)
It is of course possible, perhaps likely, that Zahawie is not being entirely forthright about the details of his trip, but the bottom line is that such assumptions are pretty thin evidence to justify a military invasion.