I think it has more to do with how our emotions subtly influence how we weight what we read. We're more likely to notice the cases we dislike/disagree with and let the ones we like/agree with glide by without affecting our impression of the community. Because of this, negative impressions and overgeneralization are much more common than the data really support.
https://hn.algolia.com/?dateRange=all&page=0&prefix=false&qu...