Why is everything that China does considered bad in the USA? Even if it means bringing peace into the region.

You will have to understand USA domestic Politics in a deeper manner to understand why.

Why is China lying about an ethnic genocide against Uighurs?

There are two assumptions to what you're saying. One, does the United States think it's bad that Iran and Saudi Arabia are willing to normalize relations (i.e. reopen embassies) after ~7 years? Two, has China brought peace into the region?

They broken the relation 7 years ago only.
The war between Sunnis and Shiites began on October 10, 680 with the massacre of the descendants of the Prophet Muhammad in Karbala (Iraq) The war between the two versions of the religion of peace has lasted for more than 1300 years. No reason for this not to continue for another good millennium.

CCP is incredibly racist their party is representing Han Nationalists, they do genocide on muslims by sterilizing women and sending men/women in woring camps etc...

So both Iran & Saudis smile, shake hands, but it stops here.