IMO the death penalty is a disgrace, but it's not comparable to things like Tianamen Square. Not even remotely.
The death penalty is administered within a legal framework that is designed (nominally at least) to be transparent and afford due process. The implementation is sometimes flawed to the point of absurdity, but the American people largely know this and are free to criticize and debate it without fear of punishment by the state simply for disagreeing. (EDIT: And, more to the point, Americans are increasingly using the power of their vote to abolish the death penalty.)
I hope you can see how the Chinese government's claim to the right to slaughter and imprison its citizens at will and in secret or the crime of expressing dissent is, um... different?
> "And they consider it perfectly legal to assassinate their own citizens without anything like a trial (as in remotely, with drones, when said citizens are involved in terrorist acts)."
Who's this "they" you speak of? Obama's extra-judicial killing af Anwar Al-Alawki, for example, is one of the great stains on his presidency in the eyes of a large portion of the voting public, and it was hotly contested within the government too. And again, Americans are free to criticize these actions without fear of government reprisal. I remember calling Obama's action cowardly and illegal here on HN a few years back, and the thought of being killed or imprisoned for this never occurred to me. Exactly how does this situation compare to that of China?