This paper has now been published at the Journal of 9/11 Studies.
http://journalof911studies.com/volume/2010/Falsifiability.pdf

There is a response given by those who support the official theory of the events of 9/11 which is hard to answer. It is "I am not a scientist and cannot understand the arguments". The intention of this paper is to appeal to people who are familiar with philosophical debate but not comfortable with science and the scientific method. The paper starts off with a rather wordy study of the way we interpret information and give it weight or reject it. I think this might gently lead some readers, normally resistant to concise scientific papers, to look at, and understand, the scientific analysis which follows.

It is probably also worth mentioning that the paper starts with a reference to Milgram, whose experiments showed how remarkably prone we are to obeying authority even when the act appears inhumane. This may remind us that there are answers to that other common difficult response: "They couldn't have done it!".