It's commonly claimed that the Khmer Rouge were CiA puppets. If so, why? What reason did America have for toppling the King of Cambodia and replacing him with communists?
Edit:
Wow I don't even know where to start with that person's response:
He carried out progroms against various groups of people.
He was supported by the CIA against actual left wing movements in the region
Regardless of his very doubtful commitment to socialism, he never made any attempts to implement anything socialistic. Not even welfare capitalism that progressives like to call socialist.
I'll address your question first though, as it seems to miss a key point.
So in 1970, there was a bloodless coup that saw Sihanouk removed from his position as head of state. This was then filled by the 'Lon Nol Regime', or the Khmer Republic. While they were 'pro-US', there is very little credible evidence that this coup was carried out by the CIA. It would be quite a misunderstanding to say that this was the CIA removing Sihanouk and replacing him with communists. The Khmer Republic's raison d'etre was to fight a civil war against the communist Vietnamese and Khmer Rouge.
5 years of bloody civil war later, and the complete withdrawal of a US presence in Cambodia and Vietnam, and you have the Khmer Rouge take control of Cambodia.
So, yeah even if you want to say it was a CIA plot to get of Sihanouk, there was certainly no plot to then five years later get rid of Lon Nol/Sirik Matak.
If they were 'puppets' of the CIA, then the SS Mayaguez incident wherein the Khmer Rouge seized a US merchant ship would be a rather strange thing for them to do.
As for the other points that person raises... I dont even know where to start. Some people with certain ideological persuasions tend to participate in these mental gymnastics where anyone who was a communist couldn't do anything wrong, and if they did do something wrong then they weren't communist.
Saloth Sar actually had a commitment to communism from his time studying in Paris in the early 1950s. He believed in the kind of revolutionary vanguard party that Lenin envisioned. He certainly implemented some communist policies. He was also guilty of crimes against humanity - like Stalin, Lenin and Mao.