The admission that the pilot had never trained the escape manoeuvre for the sequence he was flying pretty much sums up the risks that were being assumed. To do so would not have taken a great deal of flight time, and could have been accomplished at a height that would permit learning from errors. Seeing these aircraft fly does not need a show of exacting skills and daring. most of the crowd can't see the aircraft when it flies down close to the ground, and noise is not particular to much other than r^4. Conducting low level aeros with verticals benefits from a level of proficiency, however smoking holes exist in various locations from highly proficient operators who had bad days. Occasionally, level demonstrations go bad, but that is most often due to mechanical failure.
No, it is not I who is 'giving a compelling basis...' It is a combination of:
a. Martin-Baker (correctly) withdrawing support for old seat designs in legacy aircraft, negating the Safety Cases and hence the airworthiness approval, and;
b. The apparent confusion caused by the CAA allowing inert seats in some aircraft, but not in others; and other EU countries mandating inert seats.
It's about 5 years since I strapped into a hot seat, (not an MB) and about 15 since last sitting in a MB seat, which was inert. In between, both live and inerted Russian seats of various voltages. MB has done what they think is a good idea, I personally disagree, but they are free to do what they do. There are aircraft that I would not taxi without a live seat, there are others that the seat is just a discomfort to the driver. In all of these cases, live or inert, the airworthiness was not affected, the operator had a choice as to what risk they were prepared to take for their occupants. As far as the CAP goes, unless thee is one that predates rev 8 that states otherwise, the UK CAA does not mandate the seat to be live, it is an election by the applicant for their conditions of the NPTF. There is no confusion in the CAA accepting one operator electing top paint their plane pink and another wanting their plain in plaid, nor is there with an election for a seat being inert or not. MB, while undertaking a CYA did nothing to further the interests of safety by denying support for what you refer to as old, and what the counter view is tried and tested. My greasy "old" wright cyclone may be old, but they are pretty well tested by time as well. Fortunately, there are parts of the world that permit the operator to determine the risk they are prepared to assume, where there is no increase in risk to the public. There are also a few other seats out there, once Vlad stops being uppity.