People are funny when it comes to definitions. You mention some completely abstract concept with no real hard meaning – something that means whatever people say it means- and people dig in their heels and say that the definition of the concept 50 or 100 or 1,000 years ago or yesterday is the only actual meaning of the word, and no other definitions are permitted. Why aren’t new definitions permitted?
Did God divine those definitions for those words? Of course not.
Let’s go lower on the bar.
Did science give us a pretty damn precise definition of those words like science has given us definitions of rocks and trees? Of course not. The Humanities are barely even sciences anyway. Physics envy is a thing and the current replication crisis is not surprising at all and is instead to be expected in any nonscientific enterprise (such as the Social Sciences).
These people seem to be engaging in some sort of magical thinking. They are confusing the words for things with the things themselves. There are words and there are things that the words represent. You can’t blur the boundaries. That’s called magical thinking.
They seem to think there is something special about words and that all words have some sort of ultimate Platonic essence or meaning and that all words can always mean only one thing and never another thing or that meanings of words can never change, as they are set in stone. Heidegger talked about this a lot. Sure, when you say the word rock or tree, you define and actual thing that’s not likely to change a whole lot, if at all.
So those words can’t be messed with – they are what I would call absolute meanings. You can’t decide that the meaning of rock is now tree, and the meaning of tree is now rock. You can, but not in a true philosophical sense. Can we say that the definition of a tree or a rock is whatever people say it is? Not really. I can’t say I’m a rock, and this keyboard is a tree. That’s because those terms have hard and fast meanings or absolute meanings and describe things that aren’t likely to change much if at all.
But what about Communism, socialism, on and on? Those words are not like rocks or trees. There’s no precise definition of what any of those are. Those are just models of political economy that people came up with and defined them by some utterly arbitrary definitions. In other words, those terms have utterly arbitrary meanings (Heidegger goes on about this at length). The meanings of things like this are more like little tags that we put on things to say a this is a this, and a that is a that. We can pull the tags off old concepts and go put them on new concepts all we want to -redefining concepts – because these concepts never had any true or absolute meaning in the first place.
Of course you could decide that communism and socialism now mean quite different models than they used to? Why not? These things are potentially ever-changing, not like rocks or trees.