I had a flat-earthier as a roommate for about half a year. We had some detailed discussions about his beliefs, which was interesting since my time at the South Pole gives me personal experience that directly contradicts most of his beliefs. The guy clear had a very poor understanding of math (especially geometry) and physics (especially optics) but was a generally nice guy with a good head on his shoulders.

I would trust very ñittle he had to say about things outside of his direct experience, since his BS detector was apparently broken, but I would tend to trust his knowledge of things he had dealt with directly.

While I don't judge people for their ideological bent, I do judge them for uncritically accepting BS because it fits their ideological bent. This leads me to dismiss many of the knowledge and opinions of people who find themselves trapped in the ideological games played by our media.