It can be argued that it is human nature to be biased. So it may, or may not surprise you that Documentaries are often biased. Some films are more bias; films dealing with politics, or tragedies, while others are less biased; nature documentaries.
Even influential minds will tell you that documentaries are not objective as Wade Hodges mentioned in his blog about Roger Eberts opinion. Eberts says
“Most documentaries, especially the best ones, have an opinion and argue for it. Even those that pretend to be objective reflect the filmmaker’s point of view. Moviegoers should observe the bias, take it into account and decide if the film supports it or not.”
This is a view shared by Wade as well as another blogger Barry Natusch is his blog.
I agree both that the audience does play a major role in choosing what films they watch, and in some way affecting which films are more popular, and therefore influencing how films are made.
I do feel that films should strive to be objective. One film that does a very good job of this is also one of my favorites. Restrepo the film makers followed a platoon of soldiers and recorded their day to day lives. In my opinion this is not a patriotic film meant to glorify war, it is simply life, and death as an American soldier.