The American left who has opposed action in Iraq (and in many cases Afghanistan before that) has increasingly latched on to the myth that "Bush lied". The theory is that Bush "sold" intervention in Iraq based on stockpiles of weapons of mass destruction in Iraq. And since we've found no massively stockpiles (we have found some WMDs just not in large quantities) we therefore (they argue) went into Iraq based on a false premise. This is total nonsense.
Besides the usual facts that everyone thought Saddam had stockpiles of WMDs (Clinton, Bush, Kerry, etc.) that wasn't why we went into Iraq. It was one of the reasons. But it wasn't the primary reason. The biggest reason was related to WMDs in the sense that we were concerned about Saddam as a long term threat, especially once sanctions got lifted (as France and Russia were pushing for).
The arrogance of the American left on this issue is immense. It is almost contemptuous of the intelligence of the average American. Even today, most Americans support US action in Iraq. The recent problems in Iraq have caused that support to dip slightly under 50% in some polls but that has nothing to do with WMD stockpiles, it has to do with frustration with US policies in the occupation. But if the liberal premise that we went into Iraq for the WMD stockpiles were true, then American support for having gone in there would be at 10% with only the hard core "neo-cons" still in favor of it. But it's not, the WMD stockpile issue was never a central premise for going in.
It bears saying it again: If WMD stockpiles were the primary reason for going into Iraq, then the fact that we haven't found any would therefore lead one to conclude that nearly all Americans should believe we made a mistake going in there in the first place. But that isn't the case. Therefore, other reasons must have taken precedence for their support.