Instead of making some sort of judgement call (this is biased in X manner), how about a tool along the lines of something I read about in an SF story a long time ago (sorry, don't recall the title or author). I remember the point-of-view character looking at news items on a screen and things like "connotation indices" and "hyperbole metrics" were included. Those sorts of indicators would give each reader a chance to realize to what degree bias exists and leave it to them to decide how important that was.