1970s intelligent young American students at Harvard favored the the Khmer Rouge.

Since the U.S. incursion into Cambodia in the spring of 1970, and the subsequent saturation-bombings The Crimson has supported the Khmer Rouge in its efforts to form a revolutionary government in that country. …

In the days following the mass exodus from Phnom Penh, reports in the western press of brutality and coercion put these assumptions into doubt. But there were other reports on the exodus. William Goodfellow in the New York Times and Richard Boyle, the last American to leave Phnom Penn in the Colorado Daily reported that the exodus from major cities had been planned since February, that unless the people were moved out of the capital city they would have starved and that there was a strong possibility of a cholera epidemic. The exodus, according to these reports, was orderly; there were regroupment centers on all of the major roads leading out of Phnom Penh and people were reassigned to rural areas, where the food supplies were more plentiful.

There is no way to assess the merits of these conflicting reports—and if there were instances of brutality and coercion, we condemn them—but the goals of the exodus itself were good, and we support them. …

The new government of Cambodia may have to resort to strong measures against a few to gain democratic socialism for all Cambodians. And we support the United Front [i.e. the Khmer Rouge] in the pursuit of its presently stated goals.

Another article "The Will of The people" concludes:

Congress and the public have come to accept that the U.S. must stop interfering in Cambodia’s affairs, which will surely result in well-deserved victory of the revolutionary forces led by Prince Sihanouk and the Khmer Rouge.