I can't tell if you are disputing or agreeing?

Obviously, in the scenario you describe, people will continue describe themselves as "anti-rapist" and everybody will understand that they mean that they are opposed to rape.

There is no "loose-knit ideology/movement" called "antifa" - there are groups like SDS and Don't Shoot PDX and a zillion others who describe themselves as "antifa", using it as an adjective. I'm aware of no person or organization who has attempted to proclaim that they are the one true antifa org.

There will never be "one true" org for groups like this anymore. There is no rational reason for a group to put a target on their back.

Leading isolated cells by social media is the new techique to cause change/chaos (depending on your viewpoint).

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.)