The "both sides do it" argument misses historical context. As little as 50 years ago, the KKK was still lynching people, and lynched about 4000 African Americans totally according to figures. After they couldn't lynch anymore, the moved on to terrorizing African Americans by burning crosses on people's lawns, and bombing churches. We just ended Jim Crow, an Apartheid system, only a half century ago, and today black people still face intense racism. I see people saying "it's a fringe" yet I can still hear people making racist comments in my own family, none of whom go to Nazi/KKK marches.
That historical context makes these bold marches a larger concern, because for every buffoon you see in that march, there are 10 "moderate buffoons", and 100 "moderate moderate buffoons", who walk around thinking because they're not a Nazi or KKK member, and don't own slaves, they're not racist, but who do hold very bias views.
These views translate into more convictions for black people faced with juries, they translate into more loan or job applications denied.
That's why a re-emboldened KKK/NeoNazi group is a concern. Dailystormer has 300,000 registered accounts, how many does Antifa have?
The US has never had a communist revolution, we haven't had people sent to Gulags or "reeducated" for failing to support The Party, or Marxism. But we have sent 150,000 people to camps for the crime of being Japanese. So radical leftists aren't exactly a scary threat, they seem even more buffoonish by far, the dead-enders still calling for communist ownership of everything.
So when I read right wing media reports about the so-called history of left-wing violence, I'm not very phased. I would be scared if say, I lived in eastern Europe.
But white supremacists are much more realistic threat to the US social fabric because so many people hold racist views, either overtly, or implicitly.
Imagine an Islamic theocracy which turned secular over time. Suddenly, religious conservatives are emboldened and start huge marches, and some violent opposition groups emerge. Should the majority of the population be fearful of the opposition, or a retreat back to a religious theocracy which say, 50% of the people in the rural areas aren't opposed to?
Historical context matters a lot, and the giant racial scar that still hasn't healed in America means that Antifa and the KKK are no where near equal in concern or guilt for damage to the social fabric.