Don't matter how amazing and old the Tibet civilization was, other civilizations of the world (as Lakotas) also deserve to be free.
At least Tibet and Uyghurs are provinces in China with some grade of autonomus power, meanwhile Lakotas don't have even a state of United States to claim soverign.
The unique Native American States of USA, Oklahoma, have more white population then indigenous. And when they try to break the Oklahoma state in two (one of more native americans and other with more white americans) it was dennied by US governement.