[huahaiy]

Chinese govenment's justification in Tibet is mainly legalistic, as follows: Tibet was a part of the Qing Empire. Qing handled over all administrative power peacefully to Republic of China. People's Republic of China overthrow Republic of China, therefore inherits all of its administrative rights. Of course, the later part is muddier because officially the civil war is not over.

On the ground, for the people, the real justification are different. It used to be the liberation of common Tibetan people from a regressive serfdom and a brutal theocracy, not unlike the communists' justification for themselves elsewhere in China. Similarly, after Deng, the justification is more about improving people's economic status and living conditions.