“Tankie” is a caricature. The idea of a tankie is the ideal vision of a McCarthyian Communist. In reality, the overwhelming majority of people labeled as such don’t actually fit that label, it’s more of a way to cast an image of someone’s positions based on, say, support for AES countries, and twist that into the evil Commie Pinko that haunts the dreams of 1960s children in the US.
Moreover, calling Communists "fascists" makes about as much sense as libertarians complaining about the US government being "Communist." It's entirely divorced from reality and rests upon dramatic errors in understanding what fascism is, and how AES states are run. I recommend reading Blackshirts and Reds to understand why fascism and Communism are in no way comparable, as well as Is the Red Flag Flying? The Political Economy of the Soviet Union to see how the Socialist economy functioned in the USSR.