The uprising was a CIA backed coup attempt, confirmed by the CIAs internal documents. I don't know how else to tell you that you're using the empires rhetoric against fellow leftists. Disagree with tankies? Fine, cool, I'm down to oust them too, as soon as we overthrow the empires. Until that happens, there is no difference between you and a tankie to our common enemy.

From the article, because you know who used it but not why it was used:

"tankie” was initially used to describe the Communist Party of Great Britain, which supported Nikita Khrushchev's sending the Red Army to put down the 1956 Hungarian Uprising.