I'll never understand why folks keep talking with such dummies. No matter how hard you try to explain they will not agree with you so just cut the conversation and continue doing your thing.
I don't have time to watch the video, but being able to do something and being able to teach it to someone else are two entirely different things. Especially when the goal is that the pupils don't hurt themselves.
If you'd watched the video then you'd realise these aren't "pupils", this is a guy with a lot of experience in the sport passing on tips and help to the local kids at the skatepark. That is exactly how people used to learn this sport before it being mainstream and how a lot of people still do I'm sure. He is more than able to give kids help and they will appreciate it a shit load coming from someone obviously good at the sport.
Also the goal in skating is never to "not hurt yourself", sure ideally you don't want to hurt yourself but it is a sport that when learning you are inevitably going to hurt yourself and you need to accept that. On the whole your take is pretty shitty man.
I skated for years and wish someone older, especially someone with the kind of experience this guy has, had been around to give me tips or even just encourage me. All I had was magazines and a few videos to try to emulate.
That's a stupid take. Yes, not everyone is as great of a teacher than someone else, but an expert in something will always be able to teach someone who's inexperienced in it in some ways. By your logic no one should ever teach, or even do parenting.