You could just tell them that supporting Russia and China is bad, or that those are authoritarian regimes, and cite sources, rather than dismissing them out of hand, based on what the surface level interpretation of their arguments are, you know?

We have more than a one word limit here on Lemmy, people can respond with thought out rebuttals, rather than one word dismissals. It's just that the one word dismissals are easier to write and understand, so they're more likely to get thrown at an argument early and then up votes after someone skims a long ass set of paragraphs.

There's not like an either-or option there, I also really question your "well if we don't discard tankies then we're gonna have to discard all communists, and how would you like that!". That doesn't make any sense to me. Your "Pick one" is a false dichotomy. People are capable of more nuanced conversations, just labelling people and throwing around out of hand dismissals isn't going to be helpful in actually working out anything, convincing those people, or convincing bystanders. Even if you were to convince bystanders with such a tactic, you'd be convincing them in a bad faith way where they don't fully understand the usage of the term, so they'd be just as likely to throw it around as an out of hand dismissal without understanding what it means.

But then I suppose, you know, it's probably gonna be easier for most people to just call me a tankie and move on, right, on the basis that my argument advocating for nuanced responses and more well-reasoned argumentation is actually carrying water and "providing a smokescreen for tankies", so I might as well be one, right? Term gets stretched even further.

I have always been of the belief that if you are to respond, it better be with a well-reasoned and dignified comment, rather than just a kind of lazy dismissal. If people are doing shit that's actually against the rules, then report them. If they're engaging in bad faith behavior, you are more likely to reveal that by responding to them with good faith behavior than also responding with bad faith behavior. If you aren't going to say something nice, don't bother to say anything at all, or, put another way, don't feed the trolls.

Dunno why internet rules 101 is becoming such an uncommon thing now.