A postscript. To me - and this 9/11 thing is a good example - learning is about asking questions and listening to people's answers; it's not about poking fun at someone because you disagree with them, or a stupid shoving match to find out whose entrenched beliefs are ultimately going to win.
It reminds me of what happened with the OJ case, and no doubt several others will come to mind because it happens all the time. A snap judgment is based on a person's own views of the world and prejudices and then there's a programmed need to stick to it rigidly, almost at pain of death, for the rest of their miserable lives. Nobody wants to know the truth, they just want to win the argument.
There's a chapter in the essential book Influence : Science And Practice (R.B. Cialdini) which tackles this insane human trait of maintaining a relentless level of behavioural 'consistency', and it discusses how easy it is to manipulate and influence through this. The truth is, we really are way too precious about our personal opinions and beliefs.