Wow,
The youtube video is so ironic. He is able to post those BS on youtube from the West while youtube is banned in China. HAHAHAHAH. What a hypocracy. If Chinese have nothing to loose or hide, why ban a vital source of information, youtube, in China?
So I'm not impressed with your video link, a Chinese who thinks he knows all, hiding in Western freedom of press and media.He quotes old dynasty which can create a whole new subject for debate. Mind you, he's hiding the fact that  few Tibetan kings also conquered modern day Beijing long time ago. How far do you want to go? Tibetans don't claim Beijing as a part of Tibet, so why bring history during which there was no clear boundaries. What makes you think, if you claim that, China is NOT a part of Mongolia, since Genghis Khan conquered them.