Should not so much be viewed as a terrorist group—although they clearly are that, albeit not seriously yet—but rather as the public “face” of a political cult. Look at them: they ARE faceless, but they are all matching to the best of the same demonic, anti-human drummer.
Cults of all sorts proliferate when the old beliefs fail. It would not, I think, be overstating the case to say that the goal of Communist infiltration, subversion, and propaganda is to enable such cults, because they betray a complete failure of common cause and common purpose.
Communists dictate, and shoot or torture those who disobey. True Liberals negotiate and persuade, and any force which can disable that process helps the actual fascists, who the Antifa cult support and publicly embody.