In reply to the flagged reply:
1. While the Constitution of the People's Republic of China does protect religious freedom, this is only under the condition that the religious beliefs in question do not disturb the social order, cause bodily harm or obstruct the national education system. That means in practice, people will be detained for beliefs that are considered too extremist.
2. Would you believe me that they exist if I called them "education centers" instead? Try searching for 教培中心 in http://www.xinhuanet.com/politics/2019-03/18/c_1124247196.ht... It is described quite clearly that people can be brought to these centers even if their extremist beliefs do not otherwise amount to a crime.
3. I specifically brought up "杨永信" and "豫章书院" because they don't involve minorities. I didn't mean that they were mainstream in the sense that most people would approve of their methods, but there's definitely widespread concern about students spending too much time on the internet and too little studying. It's just that most schools take a less brutal approach to the problem and confiscate their student's phones instead of using torture.
Given your statement that
> Many Chinese people hope the government put an end to "杨永信" and "豫章书院", but I don't know why they don't.
consider that many Uyghur people hope the government put an end to the conditions in those "education centers" and don't know why they don't.
4. Do tell me if any of this is unconvincing. I'm still working on an airtight argument that is acceptable for someone with the perspective that the CPC is trying to do good in principle.