You are quite right. Among the most absurd claims of the right is that the left in this country is some how responsible for the genocide in Cambodia. First off, we were not officially at war in Cambodia so withdrawal from Vietnam is irrelevant. Second, no one from the American left told Pol Pot to murder 2 million people. Third, as you point out, it was the CIA sponsored coup that made the Khomer Rouge takeover possible. They weren't popular until Sihanook, the deposed prince, started to broadcast his support for them after being ousted in the coup.

The country that stopped them was communist Vietnam. They invaded Cambodia because they were tired of the flood of refugees coming across the border from their insane neighbor. The last thing I would point out is that in support of our own political ends, we killed about 1.5 million Vietnamese. What makes this killing for a political end so much more palatable than Pol Pots? Maybe because it was performed from high altitude with B-52's