This works in a courtroom. This won't work for a politician who retweets a faked video that then incites real violence. And that, at least for now, is where we truly need to be concerned.
Does it though?
Suppose there is a theft at a company. The police go to the company's security team and get the surveillance footage. Presumably admissible.
If it was an inside job, the surveillance footage could be a deepfake showing someone else committing the crime. Or maybe it's real surveillance footage. Without some way to distinguish the two, how do you know?
To rip from current headlines: https://www.justice.gov/usao-wdpa/pr/erie-man-charged-arson-...
(Leaving aside the merits of the case / opinions, and just using it as an example)
".. the [Facebook Live & coffee shop] videos depict a male – with distinctive hair to the middle of his back wearing a white mask, white shirt, light blue jean jacket, black pants with a red and white striped pattern down the side and red shoes - setting a fire inside of Ember + Forge."
"A review of additional Facebook public video footage from the area of State Street near City Hall in Erie on the evening of May 30, 2020, shows the same individual without the mask but wearing identical clothing and shoes. The subject’s face is fully visible in this video footage."
And that's a federal arson charge (min 5 years, max 20 years prison).
Ultimately you end up back at the beginning: holding people, and not pieces of information, accountable for their actions. That's an issue with civil society, not social media.
Plus, deepfakes have the potential to create much more noxious videos than real life. Real life videos depict real life people, flaws and complexities all included; deepfakes will be constructed to depict representations of the target that're most likely to generate inchoate rage of the mob. It's rare that the former happens to be exactly the latter.
Why not blame the person who confirmed your husband's death at this point if accepting comfortable illusions of someone easy to punish is what we are doing? Without them you would still have some remote hope of survival!
The first step of solving a problem is recognizing the actual problem - what we find comforting is only a distraction for rationalization purposes. Better to recognize that microscopic organisms caused the crop failure instead of burning an old woman as a witch.
Politicians don't have a particular right to remain in office despite inciting violence, even if it gives them the sads if they face repercussions.
If the video weren't fake, would that somehow make the murder of Rohingya acceptable?
Just one example: A radio station (RTLM) in Rwanda laid the groundwork of genocide by dehumanizing Tutsis, among other things by referring to them as "cockroaches" repeatedly. The station was deemed instrumental in the resulting murders of at least half a million people.
It's not fear mongering to look at the facts of history and see that propaganda is a primary way that violence scales. Deep fakes are another tool which will certainly be used towards these same ends. What propagandist would not want to use such a tool?
Propaganda is a primary way that human action and organization, whether violent or not, for good or ill, scales.