Easiest dunk is to show that the West REFUSES to let communism “fail” by itself. If socialism represented a bumbling oaf of a society, it would inevitably stumble and collapse of its own accord. No need for attacking Grenada, Vietnam, Laos with open warfare. No need to assassinate Allende or the many socialist politicians that were killed. No need to send armed forces to stop the Russian Revolution. If socialism was purely set up to fail, we wouldn’t see the PRC rising to become a major world power, etc. I could go on, but basically if it will fail, let it. Obviously the west doesn’t let it because it’s a shitty argument from the start, I GUARANTEE you that nobody (high ranking at least) in the US gov genuinely believes this. Maybe a few dumbass senators or Reps but Foreign Policy advisers, CIA/FBI, they understand that socialism is not going down on its own
We can debunk it, but that would involve the party making this claim actually having to read, think, and challenge their past assumptions. They may well do that in some contexts, but not when they're arguing in bad faith and parroting stupid lines like this one.
It’s a silly argument because it’s basically unfalsifiable. You could lay out the most rational argument for communism and it wouldn’t matter because it’s all just words on paper. It also just kind of ignores the fact that plenty of communist theory has yet to be written. We have to go through a scientific process of experimentation to figure out how to build it. We can hypothesize about how it could work but none of that is set in stone.
There's nothing to debunk because the claim itself is based on an absurd level of ignorance, they don't even know what they mean by the word communism, and it makes no sense for it to be "tried". The only consistent references that could almost make sense are these
Communism as a theoretical state of being (classless etc society) posed by me Marx (and some others) as the eventual project and outcome of the dictatorship of the proletariat. As such, it has never been "tried", it can't be "tried", it is more of a goal or state of being rather than a strategy you can adopt. Plus, that project requires that the capitalist class be deposed by the working class such that efforts in that direction could be enacted, which unfortunately has been limited by the extreme and violent reactions of imperialists. It's difficult to do that project when you're just trying to survive the sanctions and wars.
Communism as in a country run by a communist party. This has been tried, and to great success, with fantastic improvements in quality of life for those living there. What failures we do identify largely fall into two buckets: (1) targeted for destruction by imperialists and they were forced to succumb or (2) fell apart through the former and internal failures to build a robust political system, e.g. someone like Gorbachev should never have even been near the reins of power. Both can be criticized, but neither can be chalked up to, "oh dang commies can't run countries". Alsi, the largest real economy on the planet is run by a communist party and overcame over a century of colonialism and then industrialization to do it.
But really, someone saying this isn't even speaking the same language as us. It's really a conversation between two clueless liberals: one that simplistically craps on "communism" and it "failing" (without pointing to anything concrete) and the other liberal trying to say things like, "well real communism has never been tried".
In both cases, they're in need of a basic education, starting with, "what is a communist?"
Universal economic prosperity does require more than communism, just like an engineer must know more than just geometry. But engineers who deny the law of cosines tend to build shitty bridges