Well, what you said is nonsense. Usage of a word can't possibly define it. If it could, then it would be impossible for someone to use a word in one way but mean something else. Yet they can, because meaning and understanding are more fundamental than words are. Plus, once you give up the ability of words to be defined prior to its usage, words lose their power and meaning. Consider that Trump says whatever he wants, then later claims that people are misinterpreting his words. He and his followers haven't changed the definition of words. They're just abusing them. And that's what politicians do.

Also, useful knowledge has the tendency to resist being destroyed. The original definition of liberalism will never be deleted from the word itself as long as people contjnue to study and speak English. And to be real, probably what will happen in the future is that this current political paradigm will be called something like "late 20th century American liberalism", with the original word returning to its former self.