Actors faces are already public. Then again,I would probably be pissed when my face would be used as a mask to say something I might not agree with. Interesting question if that is ethical or not.
There's a long history of this kind of masking:
- Backlighting, with the face in deep shadow. Possibly with the original interviewee or an actor.
- Voice-Masking with some kind of voice-changer
- Using a voice-actor to say the words.
I would see this as the next evolution of this process.
So long as The actor being portrayed has given their consent to do this (they were hired for this specific job), and the facial expressions/behaviors are genuinely recreated I don't see any ethical or moral issues.
It's likely not ethical, and I'm confident it's probably illegal. For example, can you setup a billboard at the side of a highway with Tom Hank's face on it and a quote that speaks to anti-trans rights, has a homophobic remark, or perhaps an anti-CCP statement? Probably not.
I'd say this is no different.
IANAL, but in the US you'd need (a) rights to the image being used (e.g. shot yourself, in public) & (b) a damn good argument that your juxtaposition of their likeness and your words doesn't cause them monetary damages (e.g. in the form of lost revenue from reputation).
Well... "need" is, as I often say, quite a strong word.
Might makes right, and money talks, so if you don't want to bother getting the rights, or the person who you want to exploit can't fight back, why not?