Because people feel the need to be correct and will try to defend their opinions at all costs instead of considering all the information.
Discussion
And nostr is a particularly bad case if this? Dunno. I think you can just ignore the bigots.
Or expose people for their poor behavior. This missus here for example. Prefacing statements with "I'm not a climate scientist, but ..." promotes an idea of "ignorance is strength". And "I find the omission interesting" is implying criticism instead of expressing it to allow backtracking later.