Since I don't watch TV or read the newspapers/magazines, none. Even a sportsperson advertising sports equipment doesn't convince me of anything. Nor does wannabe intellectuals presenting trivial media articles in the guise of asking a question, minus anything resembling an individual thought or opinion.
"Celebrities are generally known for having little in the way of grey matter". Such a gross and inaccurate generalisation is indicative of your reading and viewing material. Sharon Stone, for example, has an IQ that puts the majority of doctors to shame.
Isn't this one of the arguments that you bag ... an appeal to authority? You really do tie yourself up in knots with these arguments that you just mimic. A lot of the people that you and others bag fall into that category - "highly educated, trained and qualified professionals accredited and registered with your government". In fact, far more non-medical people than medical fall into that category.
A waste of 5 points!
EDIT: Oh dear, pulling teeth is a piece of cake compared to the monumentous task of getting you to see the hole you have dug yourself. You are saying we should all listen to doctors just because they have a perceived authority. And some of them are dumb as dog crap, don't even have the equivalent common sense about health as the average mother. Passing exams isn't the same as being effective at what you do. IQ is a very basic measure, and fails to incorporate the majority of human success factors.
One of the professed doctors in this forum, in response to a question about how to cure a toothache, gave the advice to have it pulled out, despite the well-known medical facts that toothache isn't always related to problems with teeth, and that there are a range of possibilities and solutions for the toothache. Then, when the ignorance or laziness of the answer was pointed out, responded "whatever". That is not someone to whom people should be trusting their health.
You made a gross generalisation about celebrities' grey matter that is as ill-considered and ignorant as any generalisation about race, colour or creed.
I'm not the one to be embarassed.