I read the article you're linking to, and I don't see any allegations that the 900+ false statements were known to be false by the administration at the time[1]. This particular article certainly doesn't meet my standard for "[showing conclusively] that they lied, that they lied knowingly, and that that they lied a lot". Perhaps that evidence exists in another form, but I think you strengthen the GPs argument by presenting this as definitive evidence when it's not.
Addendum: The money quote from the Center for Public Integrity and the Fund for Independence in Journalism run study is this: "In short, the Bush administration led the nation to war on the basis of erroneous information that it methodically propagated and that culminated in military action against Iraq on March 19, 2003". The use of the word erroneous here is problematic. It doesn't imply intention. If they had used a word that implied intention, then they would essentially be saying that the administration intentionally propagandized with information that they knew to be false toward the goal of leading the US into war with Iraq. But they don't go that far. They use the word erroneous. IF the administration was unaware of the eroneousness of the information, then there's no reason that "methodically propagating" it is immoral, I mean, this is called "consciousness raising" in other contexts. Perhaps the authors are just being cagey so as not to paint themselves into a corner, but this is not a clear statement that the administration lied.
[1] Perhaps my reading skills aren't up to par, and I missed it. If so, let me know.
[edit 11:06 CDT to add addendum]