I didn't mention prescriptivism, I only mentioned descripticism

My mistake - I'm muddling my prescriptivism / descriptivism terminology (I'll edit the terms in the post)

The usefulness of words comes from their understanding, not their use. If you use 100% valid dictionary words but not how people commonly understand them, then you're failing to communicate.

It doesn't make me any less correct or them any less wrong though.

In this case, you have a definition of communism contrary to how people understand it, so you should either clarify your definition of it, or not be so attached to the word that you insist on using it.

I've given a key reason why they're wrong (lack of worker enfranchisement), and pointed to the dictionary for my definition - any credible one will do, if in doubt, use the OED.

You're not seeing your hypocrisy here though - you're not talking about definitions - you're talking about labels. People calling China communist isn't a definition that I can measure other countries against - it's a label entirely devoid of meaning. That's meaningless, that's a failure to provide a definition, and that would make me straight while secretly getting railed by those hundreds of dudes - even when 100% of the people saying I'm straight (making it true to what you call a descriptivist) would say that behaviour makes me gay (an actual descriptivist definition).

What are the characteristics people are pointing to when they say China, the USSR and DPRK are communist? This is what a descriptivist definition is.