Horrible acts are occasionally better than the alternative, if you think of the number of lives lost compared to the number of lives saved.
I am not sure that these actions by the Chinese government are perfectly justified by this argument. But I think it's possible. Often, governments fall and civil wars start from a tiny spark of seemingly innocuous political dissent that grows out of control. I am sure you'll find many examples of that in history.
The stability of Chinese society, just like the stability of any modern society, is always hanging on a thread. You may just not realize it because you (I hope) live in a country that is not drowned in blood. A small problem can easily grow into a disaster, and then no one can stop it -- look at Yugoslavia, Syria, Somalia, Yemen, Eritrea, Libya, Sudan, Congo, Liberia, Georgia (ex-USSR). And these are just the ones I remember watching live, in disbelief.
About organ harvesting.
From what little I read about it, prisoners may be executed, and their organs given to people who need them for medical reasons. I assume you're not against organ transplantation, since that saves lives at no cost to their original (dead) owner. So I assume you're only against the execution of prisoners.
Opinions on capital punishment vary, even in the US. What's viewed as fair and just penalty in California or Florida, has been viewed as unreasonable cruelty and violation of human rights in Maine for well over a century. Of course you're right that in the US, most people would not be ok with executing people for political views (except state treason), and even less so if the execution is timed to make their organs available to others. However, I think you could allow a larger difference of accepted practices between two completely different countries than between states of the US.
It seems that you are arguing in bad faith. The problem with organ harvesting isn't that they harvest them from those sentenced to death; it's the discrepancy between number of operations and organ availability and number of capital punishments.
In a country like China, US, or Russia, it's much harder to stop a civil war or chaos, and the damage from that is immeasurably greater. So avoiding it is really important.
I didn't understand what you meant about the discrepancy. If you don't mind explaining, I'd appreciate.
It's easy to excuse horrible acts by saying it's for the greater good, but it's rarely actually the case. Chinese civilization won't collapse if they stop harvesting organs and imprisoning people who are even mildly critical of the government.