IMHO there's a few things you have to consider. First there's the issue that documentaries are a form of art. One way that art, at least for me, defines itself is that it's unique because of the artist. If 2 very good crafts(wo)men paint a wall the result will be (more or less) the same, if two artists paint on the same canvas the result will be significantly different even if they try to paint the same picture.
Now compare documentaries to journalism. Even when journalists do their best to be impartial the results aren't always, there's always personal, religious, cultural biases, there's the stress of deadlines, there's the wishes of the editors or sponsors, there's the conscious or subconsious choices you make to cut things out of the story, highlight other things, for the sake of clarity but which end up "coloring" a story.
Now, even though it's a gross oversimplification to say journalism is purely a "craft" and documentary making purely an "art", one can assume that the personal "coloring" is even a bigger issue in documentary.
So I personaly think that, no, documentaries or journalistic pieces are never fully (or at all) unbiased. This is not an issue for me. I very much like to hear the personal in the story. For instance, when I read a piece of N. Chomsky, I don't think, now I will know the truth and the whole truth about this subject, I will rather think, now I know N. Chomsky's take on this subject. (Though sometimes I forget and have to remind myself, and so does the general audience, but this is another topic altogether)
Now, another issue to consider is the following, documentary makers are not always trying to cover a story, sometimes they are trying to change the world, the society, people's believes. I have not seen OutFoxced, but Micheal Moore, for me, is very much an activist filmmaker. I might agree with his messages, but I don't assume he will give me a biased account of what even he perceives as the truth. To make the power of his story stronger will he use material that supports his story and leave out material that gives a different opinion.
Again, I don't think this is bad. A film like SuperSize Me, in which the filmmaker eats at McDonalds for a month and becomes a repulsive monster might be infantile to some, but can be quite entertaining and potentially life-changing for others.
"Can the editing in a film or television programme change reality? If so in what way?
Can the way something is shot change the reality of a situation? If so how?"
Both editing and shooting can change the reality in 1.000.000 ways. In my native Iran there's regular anti US protests, but always shot in a way to hide the fact that these are actualy small groups protesting. A huge anti US protest is good for both Iranian media as well as foreign media.
Now imagine you are filming a neighbourhood, everything decision, from material you shoot on, framing, music, editing, etc. etc. changes the story. Imagine a grainy home video type of image going over the graffiti, while the soundtrack is gangsterrap. Now imagine filming on oldfashioned 16 mm, made even warmer in post production, with beautiful music (think wonder years). Same neighbourhood, but two totally different emotional reactions to the footage.
Anyway, one could go on, but I hope this helps.