Also look at Gordon Vette with the DC-10 crash on Mt. Erebus. He did quite a lot of research into the psychological and physiological aspects of human perception in order to show that it was quite possible for a pilot to fly straight into a mountain in VMC. He wrote a book called "Impact Erebus" which is quite an interesting read. He was a professional pilot, so in that sense not an amateur, but he was an amateur when it came to human psychology and perception. His arguments had no effect on the official investigation report, but they did have a large influence on the inquiry.
In the end, what distinguishes a professional from an amateur is that professionals are paid for their work and amateurs are not. Anybody who takes the time to learn about a topic and ask the right questions can in time form valid opinions on that topic. If that were not true, then there would be no professionals.