Let's define "tankie" as a Marxist-Leninist who emphasizes a vanguard party that makes dictates for a whole country's economy, approves of the silencing of dissent, and excuses the practice of using force to keep an alliance together and ideologically coherent.
Wouldn't you think that such a person would naturally seek out positions of power, and have the guile and discipline to mask their intentions until they achieved those positions, so as to be more effective? Certainly it should be possible, 70 years after Joseph McCarthy, to imagine a ML making their way into a prominent position.
Also, where are the Jeffrey Epsteins of Cuba, Vietnam, and China? I left out the other two because Laos is underdocumented and North Korea is opaque. This should be easy for any serious anti-tankie to give examples of.