I take it as being an implication of your statement Will Fraser that you do not consider yourself to be a dullard.
Of course you wouldn't. So, says you, CVidRs would be O.K. ......
Given the history of the abuse of CVR and Data Recorders of all types your ignorance might be considered in some circles to qualify you as a bit of a dullard. Would you consider that to be "fair comment"?
I agree, of course, that CVidR's would of considerable technical assistance to investigators of all types (including abusers). But that's just a good technical argument. Just remember that way back when VCRs were first introduced some people thought that their presence would concentrate the minds of the dullards, etc. Same with the introduction of Flight Data Recorders. But "dullards" are in the mind of the beholder and they will always be with us.
The dullard argument is pretty weak but, far more importantly, the risks and dangers are immediate. All previous promises by airlines and ICAO and many states about date protection were broken on several occasions. Why would it be different for CVidRs?
Answer: it would not.