Do you? Consider for a moment all the dissidents and protestors who would be ensnared by their own devices then, with no "it was all ai" defense available?
I don't think the lack of a durable chain of custody really provides any protection - that protection needs to come from a strong legal system and social contract to protect whistleblowers. If you're thinking of, as an example, an Iranian smuggling out protest footage, they're already taking an extreme risk and have a state using numerous tools to try and track them down - but the lack of a durable chain gives a wide area of authorities to cast doubt on the truth.
I think your question is interesting to ponder and I think there are arguments in both directions - but my mind keeps coming back to the tank man photo being smuggled out of China and how much more difficult it would be in the modern world for a single image to carry such weight.
That social contract is quite a bit of a hit&miss if you look at countries across the globe. Same for the strong legal system. Other concerns aside, does this not make the whole approach a non-starter?
creating a fake video about a protest is going to upset those that want to hide the protest just as much.