An excellent understanding: 3 degrees in aeronautics and astronautics and a 40-year career in aerospace doing system engineering and concept development, mainly involving applied physics. When it comes to cosmology, there's plenty to question and people have written books on the subject. What is more to the point is what your understanding of physics is.

You concede the first 5 minutes are crap---so I should press on? No. The first five minutes are crap. Your job is to clean up aisle 7. If this ignoramus can be dumbfounded by simple observations that are easily understood, why should I spend any time at all to listen to him? He has less understanding of physics than the common 5th grader.

Something so momentus, fundamental, and radical as a flat Earth can be shown by at least one key fact. It shouldn't take 8 hours of brain-wiping. It shouldn't even take 8 minutes.