Sometimes, antifascism takes the form of violence. The above middle-aged woman is swatting a neo-Nazi with her purse. Her mother had been in a concentration camp. Some people who adopt neo-Nazi or "fashy" or "alt-right" or "alt-lite" positions think they are just being some kind of anti-PC comedians. They can pretend they were being contrarian or incendiary and laugh that they "triggered" some "Snowflakes".
(Although, what's white and cold and afraid of melting, really? Who is triggered by an idea of white genocide that doesn't seem to be happening--except in the minds of sad unfuckable white boys who worry they will never be father-material, and are therefore leaving all their father-material in tissues and gym socks?)
But the language and posture they adopt however "jokingly" once resulted in the mass murder of millions of people. Full stop.
The slap upside the head is a form of zen awareness teaching known as grandmotherly kindness. It is meant as a correction to a person who is on a path that leads to great destruction of both self and others through hate, fear and ignorance.
The fascist side is about violence. The anti-fascist has learned this language and is performing an outreach. Sometimes that outreach connects in a bloody way. But the fascist way is always worse. It always is. Because it isn't confronting a dangerous ideology, but directing hate at marginalized people. The antifa resistance is defense. Even if it takes a proactive course. Because we humans have been down this road historically, and know the results of it.
I am ideologically antifascist. I don't think that people who automatically invoke MLK or nonviolence in general, understand why antifa needs to be understood on it's own terms. But if you believe that equality, representation, democracy, matter--you have to pick your side. Antifa is just "anti-fascism". Don't criticize the methods before you've defined where you stand. Or you might be judged about where you stand by how you break it down. Then judge the methods. By what they intend. By what they always have.