The USSR used to call those non-communists, regarded as susceptible to communist propaganda and manipulation, "useful idiots". They weren't ideologically aligned, but they didn't understand what the consequences of their policies would bring.
The oldest reference in the west is in 1948. There's dispute whether Vladimir Lenin actually coined the term, but none that the USSR Cold War apparatus felt it about many college kids (of any age) in the west. Lenin did call the West / Wilson an "utter simpleton" for falling for their games, and there was a Russian child's game that he alluded to that loosely correlate. So whether Lenin coined that exact term, he reflected the sentiment, even in a couple of his most famous quotes. So the phrase is valid to make the point as it has been used for 70 years to paraphrase the same idea. Whether the wording is perfectly correct in translation or not, the concept is.