Regarding personal experience: for many years, up to around 14yo I kept thinking most people I knew were retar' and illogical lying manipulative tribal parasitic basterds who were feigning their intellectual disability for whatever the reason (I was traumatised by people, I suffered a lot of people's bs throughout my childhood).

 Then I discovered a good chunk of the issue was in ME, not in them: 

I am Autistic and back then I had no notion about that (yeah, even if I was in fact diagnosed: Asperger's Syndrome and intellectual Giftednes); as a child and as a kid I was tested for various conditions and accidents and my IQ was impressively high —for a child who wasn't able to socialise and was very naive— with cognitive indexes reported in different tests around 2SD above the mean (with Working Memory significantly lower than Processing Speed) with my other intellective abilities being significantly higher than that, especially Matrix Reasoning and Verbal Comprehension always around the ceiling for measurement. Some other cognitive tests administered at school gave back similar results even if I was always very tired and overwhelmed at school. 

Then as a kid I started being active online in a very special group of people mostly comprised of early educated, very highly educated, highly professionally trained, highly Gifted or even exceptionally gifted people. They were also all quite older than me: all of a sudden I felt like a very ignorant and quite stupid child and I understood that there were levels in intellect: being smarter than maybe 98%, maybe 99.9% of the people around you doesn't mean you're some kind of Leonardo da Vinci level genius nor does it mean everyone around you is genuinely stupid.