Like, I remember as recently as 2016, that term was just used as a mocking term for weird larpers. Now, it's used as a term for people they want to purge from the left (yes, I'm using those words. How they're acting is literally the definition of purging, it doesn't have to include violence).
Tankies are usually the ones to break CIA/NED initiatives, like this person.
If our side typically argue at this level, it's no wonder they see a need to stamp us out. Over time there's just too much sense being made that any subreddit that allows tankies a voice will start turning anti-imperialist like the r/cth near the end and worldnews from time to time.