I've been called a tankie for lots of reasons: criticising Elon Musk, condemning Israels genocide of the Palestinians, opposing invading Venezuela, condemning the US's destruction of North Korea, not believing that far right American think tanks are trustworthy, calling Kamala Harris a genocide supporter, calling bullshit on the claim that Mao had one in ten Chinese citizens executed for being a western spy. Calling bullshit on the claim that Che Guevera committed genocide. Basically anything that runs counter to the average American neo-liberal's world view.

The whole point is that there isn't really any clear cut difference between "tankies" and "actual leftists" because it's a pejorative term that each person using it defines differently based on their own personal politics. Is critical support for Vietnam tankie? Cuba? Makhnovshchina? Ukraine? The Nordic Model? The Black Panthers? You'll never get consistent answers from people yelling about tankies.

one takes them seriously because the things they profess tend to be silly and they usually have that obnoxious College freshman master-debater energy.

Ironically, this better describes the people who rail against "tankies" better than it describes anyone else.

It gets thrown around too much honestly, if it was just people simping for authoritarian regimes, sure, but it really does get tossed toward anyone "too left".