Useful Idiot (noun): a naive or credulous person who can be manipulated or exploited to advance a cause or political agenda

Merriam-Webster Dictionary

The term ‘useful idiot’ has a long and storied Cold War history, often being used to pejoratively describe Western leftists who amplified and played into Soviet propaganda. Useful idiocy came in many forms, from outright laundering of Soviet lies (see Walter Duranty) to simply falling for the USSR’s disinformation and false narratives. Some in the latter category still exist today and seriously argue that, for instance, Julius & Ethel Rosenberg were not actually spies (apparently they have not seen the Venona Files). Most of these useful idiots were on the political left, but the main thing that their politics had in common was a reflexive anti-American bent. Useful idiocy as a relevant political concept fell out of favor at the same time the Soviet Union did, and most thought it relegated to works of history. Now, just as Great Power conflict has returned with a vengeance, so have the useful idiots.