I someone knows how they like their hotdog, and want you to do exactly that, then it doesn't matter if you are 3 star Michelin restaurant chef. You don't know better. It doesn't matter if you devoted your life to the perfect hotdog and got PhD in hotdogology. You don't know better. If a person knows what they want and want it that way it is perfectly acceptable. It isn't acceptable to pretend you know better.
The australian in your example may just like the accents other foods give to his vegemite. They will all taste like vegemite, and if they like that, that is perfectly fine. You can wonder about their taste all you like, but that is just your problem.
Encouraging people to go beyond their comfort zone is fine. Thinking you know better than them is just arrogant.
There is absolutely something wrong spending millions on the search and rescue of a bunch of idiots who signed disclaimers and could easily have paid for a safe sub several times over. It's not the equipment used that is the issue it's the effort at all. Those billionaire morons simply don't deserve the effort, nor does it make any sense to have even tried. Unless their estate is footing the bill, but that sounds far fetched.