The essay I want you to read is called "Debunking Conspiracy Theorists" and subtitled "Paranoid Fantasies about Sept 11 Distract from the Real Issues". During some earlier research, I had found links to a broken version of it -- a huge file, in which the same few paragraphs were repeated over and over. (Imagine the film "Ground Hog Day" as a PDF file, but without Bill Murray.)
Finally ... this link leads to a much better version of the essay. It's not perfect, but at least there's no repetition of material.
Like much of what you find on the net, it could have used a good editor. There are many mistakes in spelling and punctuation. But the author, Gerard Holmgren, attacks the issue from a unique and very clever point of view. It makes for refreshing reading. I'll quote a few paragraphs here in an attempt to entice you...
[I]ts hardly surprising that the events of Sept 11 2001 have spawned their fair share of [...] ludicrous fairy tales. And as always, there is - sadly - a small but gullible percentage of the population eager to lap up these tall tales, regardless of facts or rational analysis.
One of the wilder stories circulating about Sept 11, and one that has attracted something of a cult following amongst conspiracy buffs is that it was carried out by 19 fanatical Arab hijackers, masterminded by an evil genius named Osama bin Laden, with no apparent motivation other than that they "hate our freedoms."
Never a group of people to be bothered by facts, the perpetrators of this cartoon fantasy have constructed an elaborately woven web of delusions and unsubstantiated hearsay in order to promote this garbage across the internet and the media to the extent that a number of otherwise rational people have actually fallen under its spell.
Normally I don't even bother debunking this kind of junk, but the effect that this paranoid myth is beginning to have requires a little rational analysis, in order to consign it to the same rubbish bin as all such silly conspiracy theories.
There you go. Now please read the whole thing.