It's not an organized group. It's a label being used as a cudgel to attack anyone who doesn't like the current president (who also happens to have the world's most fragile ego/thinnest skin/whatever his soul crushing pathology actually is).

It's not a group. There are several smaller orgs that call themselves antifascist but there's no such centralized group or political structure. It's not even a specific ideology. It's just oppositional to fascism