The Chinese government is no doubt guilty of severe human rights abuses in Xinjiang, but the Chinese have had (an imperial) presence there for more than 2000 years, and the area was fully 'absorbed' into China in 1759. That's just 52 years after Scotland lost its independence in the Acts of Union. It's actually the same year that the French were cut off from Quebec in Canada, and the Canadiens were 'absorbed' into British North America. Many of Russia's non-ethnically-Russian republics were absorbed into Russia in the 19th century (and many willingly). Hawaiians were forced to join the US in that century as well. There are many instances around the world of peoples of different ethnicity/religion/culture being absorbed into larger nation-states, willingly or not, and many of the ones we don't question happened more recently than Xinjiang.