There was a point when Photoshop wasn't well known, and people fell for all sorts of manipulated images all the time. Now, years later, it's common knowledge that photos shouldn't be trusted as evidence. These things are all cyclical.
Once "deep-fakes" become mainstream - how long would it take for the public to become aware of them? A week? A month? Any fake video of consequences will be immediately ripped apart by mainstream and social media. Why would 'deep-fakes' be any worse than what is being done with CG today?
I do believe that some people will fall for them, but the damage won't be any worse than when people fall for shopped images and phishing emails. It's just something we have to deal with.
The real issue is a large number of people suddenly distrusting real video evidence rather than those few who were already susceptible being led astray.
Good point. I strongly suspect the worry about deep-fake videos is overstated. Yes some people will fall for them, just as some people fall for photo-shopped images and Nigerian email scams but that's just par for course - we'll have to deal with that. Also, it isn't like videos can't be faked today with out-of-context edits, CG, and audio manipulation (e.g. dubbing).