I personally can't stand stunting as a sport/pastime, it makes all motorcyclist look bad when the monkeys do this on the public roads, which is inevitable. However, I remember tons of things I was into as a "stupid kid" that other people frowned upon. This is a common generational gap that will keep repeating itself as long as humans exist.
Regarding the video - that guy just sucks at stunting, period. Doesn't matter what he's on, he would look just as stupid doing that on a Grom. When you suck at something, don't call attention to yourself, that's the lesson from this.