There is no singular group called “antifa”. It’s a movement of loosely (at best) interconnected but independent, antifascist groups.
Also, we need all these groups. It’s them who usually organize rallies against racism, fascism, antisemitism, inhuman law proposals, et cetera. Also they organize all sorts of other actions against alt right, far right and (neo-)nazis, like disrupting their rallies and standing in the way of goon squads.
Antifa groups are damn important.