Your logic is not sound. North Korea was recently described as a worse human rights abuser than Nazi Germany, by a Holocaust survivor no less [0]. In spite of this commonly-held perception, no country has declared war on them, for many of the same economic and military reasons that no country has or would declare war on China.
[1] China is not similar to Nazi because the extent of "cleansing" is not on the same scale as Nazi (even if you count death sentences on illegal cult members)
[2] China is not similar to Nazi because it does not initiate new wars against other countries (Tibet was incorporated as a result of ongoing conflicts between China and other countries for decades, so it is not really an invasion)
I shouldn't have concluded that countries are not declaring war against China is due to [1]. However, it can be explained by [2]. Regardless, I believe both [1] and [2] stands.
I think you've taken more from the original comment than was given. Only you have compared Communist China to Nazi Germany on the basis of foreign policy, so that line of argument is irrelevant.
Historians criticize IBM for helping the Nazis to identify and exterminate political and ethnic minorities, not for improving their ability to wage war. In that respect, Western companies like Yahoo and Cisco have already been caught in similar arrangements with the Chinese Communist Party [1][2]. Hopefully Google's AI center will not continue this disturbing trend.
As to the scale of the CCP's "cleansing" to date, it's hard to know - they don't release any numbers, and foreign journalists are aggressively bullied, arrested, and deported if they try to find out [3][4].
We do know that China regularly humiliates and cracks down on members of its Muslim minorities [5], and that the Communist Party regularly intervenes in the appointment of Buddhist and Catholic religious leaders [6][7].
If that is what you believe, I would encourage you to check out these two books on the subject [0][1]. Both are engrossing reads, and paint a damning picture of the regime from different perspectives.
I have taken a strong amateur interest in North Korea for years, and the full body of press, reporting, and firsthand accounts I have read would support the comparison to Nazi Germany.
[0] https://www.nbcnews.com/news/north-korea/north-korean-gulags...