"The vast majority of anti-fascist organizing is nonviolent. 
But their willingness to physically defend themselves and others from white supremacist violence 
and preemptively shut down fascist organizing efforts before they turn deadly 
distinguishes them from liberal anti-racists.

Antifascists argue that after the horrors of chattel slavery and the Holocaust, physical violence against white supremacists 
is both ethically justifiable and strategically effective. 
We should not, they argue, abstractly assess the ethical status of violence 
in the absence of the values and context behind it. 
Instead, they put forth an ethically consistent, historically informed argument for fighting Nazis before it’s too late."
https://www.washingtonpost.com/news/made-by-history/wp/2017/08/16/who-are-the-antifa/?undefined=&wpisrc=nl_most&wpmm=1