I suggest that unless you are Vietnamese, and have lived under both the Communist and the previous neocolonialist regimes, you are not competent to comment on how great a crime Vietnamese Communism was.
There were supposed to be elections in the early 1960's to determine the will of the Vietnamese people. But thanks to John Foster Dulles, who was certainly no friend of any sort of real democracy, the Americans would not allow them, and the insurrection of the Viet Cong began.
You are hopelessly naive if you still believe, after all that has been revealed to the contrary, that the US was even remotely in favor of democracy of free and fair elections in Vietnam. Certainly none were permitted during the various puppet regimes that followed the US occupation.
Vietnam was the worst American mistake since the Civil War, although Iraq is certainly gaining on it. There was no reason for the US to have gotten involved in Vietnam. The entire world would have been better off had the elections in Vietnam been held as agreed to in the Treaty between the French and the Viet Minh.
It would have certainly avoided the Evil Nixon coming to power, as well as a host of other travesties, most of them foisted on the unfortunate people of the USA by its useless asshole ratwingers.
10,000 days of death and treasure lost. Nothing gained. All the results of US involvement in Vietnam were negative. It was not any sort of 'noble cause'. It was useless imperialistic crap from start to ignominious end.