I think there's a small amount of truth to it especially when people target someone like Luna Oi, but at least for now it's in the vast majority of cases an equivalent of chud or lib etc. and historically was a term made by mostly white British leftists to make fun of other mostly white British leftists, not something to describe groups of people in the global south.
I think this is pretty similar energy to right wing ppl / libs last year claiming using gusano is racist, obviously the people who get called gusano are almost always more reactionary than people that get called tankies outside of maybe like 1 or 2 of nazbols, but I think neither in his words are frequently racist, and it's a weird energy especially as Ben Norton is a white American guy and seems more about wanting to own the people who use tankie as an insult than it is about making a stand against any racism happening.
https://unofficialbird.com/BenjaminNorton/status/1609586255641169921#m
again, libs and radlibs on twitter calling people tankie have no idea who is at the other end of their insults. they have no idea if they are white coastal elites or chinese communists or what. So black, asian, latin people are called tankie all the time by rich white anglos
libs and radlibs are probably colorblind racists who think they're calling another white person a tankie most of the time, and they probably also think it just means "authoritarian left" or whatever and don't even know about hungary.
the entire chain is devoid of racial consideration and none of these people know anything about history so i'd argue that the racism comes in somewhere else and that "tankie" isn't any more racist than some old timey shit like "pinko"