It's called rationalizing after the fact.

Crooks and Liars » Widespread confusion:

"Perhaps most troubling, the number of people who are confused about Iraq’s non-existent role in the 9/11 attacks has gone up in recent years. When Newsweek asked the same question in the fall of 2004, 36% said Saddam Hussein was “directly involved” with the attacks. Nearly three years later, that number is 41%.

Sure, Bush administration officials have been careless with their rhetoric, leading to some confusion. And sure, there were probably some Fox News viewers included in the poll, skewing the numbers.

But that still doesn’t explain a result like this one."

Psychological studies have shown that if you make someone say or write down a statement, even and especially one they don't agree with, when you follow up with those folks later, they will have changed their opinions and arguments in order to be in line with whatever statement they made.

The conclusion is determined prior, and then the brain and cognitive function scrambles to justify the conclusion, develop a pattern and eliminate cognitive dissonance.

In other words, since we invaded Iraq, the collective minds of a lot of folks post-rationalize the why of it. It's not surprising that the worse it gets in Iraq the more rationalization and justification occurs. For all the damage and the blood and the violence and countless casualties that this conflict has resulted in, the only possible justification, in the eyes of those who need that justification, is that "they started it."

Also, people are idiots.