RE: I would search the Letters to the Editor for any evidence of the claim.
On the radio talk shows broadcast here in New York, a whole hour was devoted to the so called 9/11 celebrations in NJ.
A lot of people (especially those living in Paterson, NJ ) called in to describe their own eyewitness accounts.
But then the media can always dismiss this as Islamophobia.
So, the Letters to the Editor would not be considered good evidence at all. The media will insist on a more stringent evidence — PRODUCE THE VIDEO.
If the letter writers were sought out they may have that evidence you speak of. Investigation is not easy but many people keep memorabilia of events like this.