As far as convincing a bunch of people. Consider that if Dan shows up to a judo competition and blows everyone away, thousands will be "believers" but how many will actually show up and train, and continue to train in that new way? Maybe 3 or 4. Well, the thing is, that those 3 or 4 people will just go seek out people like Dan themselves, so why should people like Dan bother with dealing with the millions of questions from the thousands who aren't going to be really serious about changing. Well, that's how I see it...
I would beg to differ on this point. How many people trained in Gracie Jiu Jitsu after watching Royce decimate the competition in the first UFC's? Tens of thousands (myself included). Many people also lived/worked/flew to Brazil (from all over the world) to learn this particular form of jiu jitsu. All you have to do is show people repeatable skill and you will attract them. Show...not tell.