So can image gen systems.
As a former VFX person, I know that a couple of shows are testing out how/where it can be used. (currently its still more expensive than trad VFX, unless you are using it to make base models.)
Productivity gains in the VFX industry over the last 20 years has been immense. (ie a mid budget TV show has more, and more complex VFX work than most movies that are 10 years old, and look better.)
But, does that mean we should allow any bad actor to flood the floor with fake clips of whatever agenda they want to push? no. If I as a VFX enthusiast gets fooled by GenAI videos (Picture area done deal, its super hard to stop reliably) then we are super fucked.
You said you can't see a legitimate use, but clearly there are legitimate uses (the "no legitimate use" idea is used to justify bad drug policy for example, so we should be skeptical of it). As to whether we should allow it, I don't see how we have a choice. The models are already out there. Even if they weren't, it becomes cheaper every year to train new ones, and eventually today's training supercomputers will be tomorrow's commodity. The whole idea of AI "fingerprinting" is bad anyway; you don't fingerprint that something is inauthentic. You sign that it is authentic.