i am going to give a Historically correct answer:

during the cold war, there was a peaceful uprising in the soviets puppet states (mainly hungary i believe).
the soviets decided the way to deal with these people was to send in tanks and slaughter the peacefully protesting civilians

everyone that was excusing the soviets use of Tanks against Civilians was dubbed a “tankie”

As I recall everyone calls communists as tankies. For example people, who prefer maoism, that cuban communism and other ones I guess.