Because many spend so much time moral grandstanding and signaling their virtue they cannot conceive of anyone with a contrary opinion to them having any valid r

Because many spend so much time moral grandstanding and signaling their virtue they cannot conceive of anyone with a contrary opinion to them having any valid reason for disagreeing, and therefore the only reason for them doing what they are doing must be because they are morally deficient and evil. This then gets reinforced by a media-industrial complex that is happy to continue to feed you points you agree with to get you to keep clicking. Disclaimer: I am not saying I support the Republican party or that I agree with them, but that doesn't change that tons of people cannot possibly conceive of someone having a different viewpoint than them being anything other than morally deficient.