It is a sad mystery to me as well, but many innocent people
lost their lives then, and I respect their memories today...
I worked in the World Trade Center,
occasionally defending the State of New York in its Court of Claims
on several floors between 82 to 86 in Tower 2; beautiful vu from there.
I was acquainted with John Perry, a libertarian Lt. in the NYPD,
who was actually putting in his retirement papers on 9/11/1,
when the first plane hit.
He was a lawyer. The WTC collapsed on him.
If I had been killed therein, I 'd certainly not desire any curtailment
in freedom of speech (however brief, for all the good it 'd do me),
as a consequence thereof. I cannot imagine that he woud have either.