Actually I do believed that we were justified in going into Iraq. As were the following people (just to name a few):
* Rep. Howard Berman (D-Calif.): "Confront Saddam Hussein now, or pay a much heavier price later ... The idea of Saddam Hussein with a nuclear weapon is too horrifying to contemplate, too terrifying to tolerate."
* Sen. Hillary Rodham Clinton (D-N.Y.): "expressed severe reservations, nonetheless voted for the resolution."
* Sen. Tom Daschle (D-S.D.), Senate Majority Leader: "raised concerns throughout the debate about Bush politicizing national security" but backed Bush and said "it is important for the country 'to speak with one voice at this critical moment' [and that] Iraq's weapons programs 'may not be imminent. But it is real. It is growing. And it cannot be ignored.' However, he urged Bush to move 'in a way that avoids making a dangerous situation even worse.'" He also "expressed reservations about a possible U.S. attack on Iraq, and he was not part of an agreement between the White House and other congressional leaders framing the resolution ...."
* Sen. Richard Gephardt (D-Mo.), Minority Leader: "said giving Bush the authority to attack Iraq could avert war by demonstrating the United States is willing to confront Saddam over his obligations to the United Nations."
* Rep. Patrick Kennedy (D-R.I.): "broke with his father", (Sen. Edward M. Kennedy), and "sided with the president."
* Sen. John Kerry (D-Mass.)
Authorization for Use of Military Force Against Iraq Resolution of 2002 - SourceWatch
My opinion on the matter though does not have any effect on the simple fact that Bush and Cheney never said that Iraq and Saddam were involved in the attacks of 9/11.