Generation(s) of Han Chinese and Uighurs get together and start having children. An act of loving subversion, if you will. At what level of mixing does the dangerous Uighur contribution become safe to you? 50%? 25%? 12.5%?
[Only somewhat tongue-in-cheek.]
The largest group of Muslims in China are the Hui Muslims (about 10 million of them). They are the descendants of the Muslims that were absorbed during conquests in the Tang and Ming Dynasty.
They eventually integrated and married other Han Chinese. They are still Muslim, but also identify as Chinese. There are also affirmative action programs for them, making it easier for them to into good colleges and government jobs.
They were also exempt from the 1-child policy.
They are how Asians are in the US, the "model minority."
Please explain, then, why race is a category used to reduce a person's numeric "trustworthiness score" in China. If one is ethnically Uighur instead of Han or if one has received religious education then one is deemed by the government as "less trustworthy" -- not because of behaviour or evidence of a crime but simply because of ethnicity.[1][2][3]
Since this score is used to determine whether freedoms are restricted (e.g. travel, communication, and forced "re-education"), it is racism.
[1] https://www.independent.co.uk/news/world/asia/thousands-chin...
[2] https://www.nytimes.com/2018/05/15/opinion/china-re-educatio...
[3] (TFA) https://www.economist.com/briefing/2018/05/31/china-has-turn...