Yep. It's amazing to see how quickly people start denying reality when they don't like someone's beliefs/behavior.
I could acknowledge that a hypothetical smart, woke, furry, trans, porn-addicted programmer that regularly makes great FOSS contributions is intelligent and capable while still disliking their beliefs/behavior.
IANAPNA either, but a solid object like a planet blocks light differently than dust clouds. Dust clouds, even dense ones, still allow some wavelengths through that planets do not. I would guess that's what allows them to be confident that it's a planet.