The difference is that China's slavery and genocide is happening today, within its own borders.

Is that true of the US? Is there state-sanctioned/supported slavery in the US? Is the US committing genocide within its own borders? Arguably not?

This doesn't make the US perfect or wonderful. We've been politically and militarily supporting a genocide in Gaza, as a stark example.

But "the US did slavery and genocide in the past" and "China is doing slavery and genocide now" doesn't make the US and China equivalent today.

And on top of that, I can go out and protest my country supporting Israel's garbage in Gaza. If I were a Chinese citizen and tried to do something like that in China, I'd be jailed.