those who defend China and USSR as if they can’t do anything wrong

I've yet to see anyone - left, right, or center - that has suggested an entire country's worth of people has never done anything wrong in its history.

"Tankie" has a real, actual, honest to god historical definition. Its not just "people who liked the Soviet system more than the capitalist system". Its an explicit advocacy for non-interventionism during the Cold War. Specifically, it is British progressives who didn't want the UK sending support to Hungarian reactionaries during the 1956 revolt.

The British media portrayed any reluctance to intercede on behalf of anti-communists abroad as pro-Khrushchev puppets who wanted to see Russian tanks flatten all of Europe. That's what a "Tankie" is supposed to mean. It's a person accused (by anti-soviet British media) of wanting a Soviet conquest of the planet.