On HN I see a lot of accusations of "leftism", which seems basically synonymous with "communism", "Marxism", and "socialism" (all of which still hold currency). It's also effectively synonymous with "woke" and "SJW" and a bunch of others, all of which are used the same way as a generic insult for any kind of progressivism.
I don't think it's coming just from ancient reactionaries. They seem to be at least Gen X, and possibly younger.