The governments are both pretty terrible, but China has been far more violent to it's own citizens in recent times than the US has. The recent non-citizen hunts and unwise involvement in foreign affairs notwithstanding, the US doesn't (currently) have a policy of ethnic cleansing and violating human rights on a massive scale on its own lands.
Fixed. US only has chutzpah to fight someone who can’t meaningfully fight back. If US was truly fighting evil regimes, it would go for Russia, China, NK and bunch of other autocrats.
[1]: https://en.wikipedia.org/wiki/Amiriyah_shelter_bombing