> there are also clear mathematical criteria that can be used to asses the fairness of a voting/districting scheme

I think this illustrates how bias thrives in generalities - with as little evidence as is necessary to advance the agenda.

Deep examination of nuances leads to an organic, comprehensive understanding, one that is rocky soil for bias.

As example: Ideological media relentlessly push preformed talking points to prevent viewers from contemplating an issue beyond the desired scope.