the history of thibet is full of endless raiding and invasions by the thibetans on there low land niehbors, though they have been conquored themselves and the very title of dalai was created by a mongol emperor who controlled most of inner aisia in the late 1500's and so depending on where in history someone chooses to begin there arguments as to legitemacy is of course less meaningfull than the facts on.the ground, same with borders attempting to magicaly change demographics, if you dont have both, you have nothing.