Perhaps because you are not in spaces where people do so, trying to make Socialism and Communism sound stupid to make other people uninterested in others that would talk about it.

It might even be a part of someone's misinformation campaign, really.
The same place had people calling themselves Muslim and trying to make others angry at them, in ways that it would increase -ive sentiment towards the religion itself.

Simply put, the moment you put a buzzword onto anything (like any *-ism), that opens it to be grouped with anything anyone might claim it to be. And that's why one needs to make sure to explain what they mean by the word, every time they want to argue about its pros/cons with others.