Non-fiction is just as viewpoint dependent. That's why they say history is written by the winners. That's why eyewitnesses to the same event will differ on important details. That's why a politician's speech will be seen completely differently by his supporters and his opponents.
I once had a young adult during the fairly early days of our war on Iraq tell me that the newspaper is unbiased.
After I stopped laughing, I said, ok: let's select a photo of an olive skinned person with dark hair in green fatigues carrying a gun. Let's further posit that it was taken in Iraq. Among the captions the editor might select to describe the photo are...Terrorist - Armed insurgent- Patriot- Freedom fighter - Rebel- Militia member - Not to mention father of four, pissed off unemployed oil rig worker, doctor trying to get to his hospital....
Objective truth is, this man was there at this time and (if witnessed) had just done this thing. All else is the framing of narrative.