A good start would be a motive for why Beijing would do a Holocaust against peoples within China.
Hitler had a motive, you can read all about it in Mein Kampf. It was out in the open. There is nothing even remotely resembling such a policy by Beijing.
On the other hand, there is a very clear motive for why Washington would spread misinformation about Beijing. So to believe Washington's story is to put on my blinders towards Washington's interests and simultaneously accept that Xi Jinping is a comic book villain. Sorry, but that is ridiculous.