[JoshuaRedmond]

It seems to me that their view of bias is limited to a per-article approach. This could make it succeptible to broader narrative bias across stories - if, for example, the news sources are selectively only reporting on muggings when perpetrated by one race/nationality/immigration status/gender over another then it'll still give a false impression of attacks by those people, as it'll be completely blind to the lesser-reported cases.