Polarization has been happening everywhere not just HN and not just in the US. Othering is a related term.
See also: https://fivethirtyeight.com/tag/partisanship/ https://fivethirtyeight.com/tag/ideology/
See also: https://fivethirtyeight.com/tag/partisanship/ https://fivethirtyeight.com/tag/ideology/
Food for thought: perhaps people treating everything as fake news is an unfortunate adverse effect of all the messaging about the dangers of not recognizing fake news.