I don't think that's a good thing, though. Right now you can catch a politician in a lie, on tape. Once that's easily faked people will just see whatever confirms their preexisting bias.
It's something more than being a skeptic - when there's no definitive proof of anything, you just pick and choose what you believe.
People who want to believe "fake news" will believe it, people who don't care, won't care, and people who think it sounds unlikely or don't want to believe it will either disbelieve it or hopefully attempt to fact check it.
To take a more positive view of this kind of tech, I think it has promise in producing satirical content.
??? Documentary = non-fiction, isn't it? I mean, would you use CGI to show someone doing something you didn't quite record them doing?