"I am a patriot fighting the real traitors who are destroying our democracy. I resent it when they call me delusional," he said.
His second mistake is to try to solve this problem by offering $100,000 to the first engineering student who can show that the World Trade Center collapsed in the manner described by the government. Walter said that the contest would be judged by a panel of expert engineers. He imagines that nobody will manage to win and so he will be vindicated.
Now, before we consider that, we have to wonder why anybody should take Mr Walter's ideas seriously when Mr Walter himself does not? Why do we say this? Mr Walter does not believe the government's story, but there is no reason why one has to believe it in order to test it. The laws of physics and chemistry governing the behaviour of towers and aircraft are fairly uncontroversial. So a decent team of engineers could run a computer simulation, build scale model, and so on, of how the government said the crash happened. If the towers don't fall down during this test then it would constitute a prima facie criticism of the government's explanation of the events of 9/11. If his panel of engineers is competent to judge candidate explanations for 9/11 then surely they ought to be able to come up with such a test themselves. So why doesn't Mr Walter simply hire his own panel of engineers to conduct the relevant test and see what happens?
The National Institute of Standards and Technology is conducting tests to understand exactly how the World Trade Centre collapsed. So the US government is taking its own explanation of what happened on 9/11 seriously and is trying to understand what happened in more depth in order to make future attacks less damaging.
So why does Mr Walter does not take his own explanation as seriously? We guess the reason is this: His explanation requires the US government to have organised a vast conspiracy that works perfectly to deceive the American people. He arrived at this nonsense not by contemplating problems of engineering but because he dislikes Republicans. He dislikes them for having confidence in Western institutions, which he lacks. Mr Walter prefers the doctrines of environmentalism and socialism to those of the free society that allowed him to become a millionaire. The US government's explanation just requires the existence of some very evil enemies, which is rather uncontroversial, plus government complacency and incompetence, which are never in short supply.
Update: Check out this debunking by Popular Mechanics of several such conspiracy theories.