A quick search indicates that there are ~107,000 architects in the US[1][2], and there are ~272,000 civil engineers[3] in the US. So, 2330 signatories is < 1%.
Get 15% to sign off, then it might get attention.
[1] http://www.aia.org/press/AIAS077761
[2] http://www.bls.gov/ooh/architecture-and-engineering/architec...
[3] http://www.bls.gov/ooh/architecture-and-engineering/civil-en...
Also note, architects are not the right people to be quoting for this. When we hired architects, they did lots of design work, but never ended up on the calculation side of the process. Explosive loads are completely different from static loads, and architects don't learn that stuff. So I imagine you have a lot of architects that don't know what they are talking about in that 2330.
If you are arguing that it was a false flag operation that flew the planes, good luck with that, but it has nothing to do with science or engineering.
http://www.popularmechanics.com/technology/design/a3524/4278...