Live or let die?
In over 20 years of instructing I have never had a student or anyone else 'try to kill me'. Anyone who has, has not being doing their job properly. When things have gone too far it has been owing to lack of a thorough briefing when it was obviously required or simply that I have let things go too far before intervening.
With regard to revalidations, the flight is not a test nor is it an assessment during which the PPL holder is evaluated for their safety. The purpose is quite simply a matter of constructive ongoing training. This should be stressed prior to flight with the pilot fully involved with what is to be flown and why. It could be that the crusty old veteran has little knowledge of the use of the GPS that they have just purchased, they almost certainly havn't practised a stall recovery nor flown on partial panel for some time but they may well have firm ideas about such things. Why not listen to them and go flying looking at what they say but also introduce your own thoughts as well.