1) Modern day China isn't Communist. It's a mixed capitalist system modeled more after post-War Japan and South Korea where government leverage over deposit and savings banks are used to further fund the development of private industry and private firms. It's the main reason why China has suddenly taken off in the last 30 years while before that, it was the North Korea of the 50s/60s.
2) The mistreatment of the native inhabitants in Xinjiang has always been an issue and existed before the current PRC (as is the suspicion of other ethnic minorities). The Qing committed genocide there (https://en.wikipedia.org/wiki/Dzungar_genocide). In a nutshell Xinjiang is the Chinese Wild West and Uighurs are the Indians and the Han Chinese are the settlers that want their land.