I'm glad you can agree to disagree in a civil way. There are always arguments for and against why Antifa are authoritarian or not. Modda told me that Antifa are a far-left fringe group (not explicitly told though) because they are mostly anarchist or communist. Commies are authoritarian, just look at what Joseph Stalin did. Anarchos are may not believe in authoritarianism, but some anarchos have some communist traits, for example Anarcho-Communism.
Although there is one anarchist group that doesn't believe in violence: Anarcho-Pacifism.
Overall, Antifa are authoritarian because of its violence, yet their authoritarianism is nowhere near obvious as the fascists.