Only to those of a particular political persuasion. Every group has their own shorthand.

That's the intent but most people know it's not true. It's right up there with "woke" and "progressive" as generic, shapeless, boogeyman words. No real meaning besides "something bad".

They're not understood, but propagandized that way.

Pretty sure most who claim the mantle of “Antifa” would welcome that Communist label, and plenty would endorse violence if it’s against the “right” people, so if the shoe fits…