What has people who claimed to be antifacists done besides oppose facists? Because I have yet to see anybody except the the government and MAGA supporters claiming antifa has done anything else.
Well, some people who call themselves antifa also use slogans like "liberals get the bullet, too".
The right's play wasn't to invent antifa from the whole close, but to imply that those kinds of views are universal or nearly so among people who call themselves that.
(To be fair, it doesn't help that the historical antifa, i.e. KPD's Antifaschistische Aktion, considered social democrats to be its enemies, calling them "social fascists". It boggles my mind that anyone on the left who isn't a hardline Marxist-Leninist would adopt the name for themselves given its history.)