They will probably say that since the Twin Towers were built in the late 60s and early 70s, Nixon had the charges planted there, for future use. They're that crazy!
I wouldn't mind seeing more treason investigations and prosecutions. That's very easy to say, since there have been NONE that I am aware of.
I had heard that the planes were built to withstand the impact of the biggest planes of the day, but that the effect of a fully-loaded jet's gas tank exploding was not forseen. That may or may not be true. Then again, I don't know of many buildings that could withstand that.
2nd and 3rd paragraphs - I agree with and you are right about the buildings not being designed for todays jets. Wasn't the biggest plane they had when they built it a DC-3?