Colin Kaepernick proves there is no right way to protest white supremacy in America.
In most part, this isn't even about that. It's about the left's tendency to allow the right to dictate the narrative, time and again, because of an overwhelming desire to seem balanced and fair to all perspectives rather than suspicious of intent. If someone's primary concern is whether or not a member of a protesting group called Antifa punched someone at a recent event and not, say, the group of several men who surrounded a black men and beat him with sticks in Charlottesville, I think perhaps that person might be exhibiting certain biases.
Guaranteed the "mainstream public" weren't happy at the Stonewall riots when a bunch of those awful homosexuals ran out of a bar (can you believe these people) to riot in the streets after smashing up property. It's still the only reason I have equal rights as an American. "You only gave us rights because we gave you riots."
The right's primary strategy for years, rather than changing or moderating their position, has been reframing the discussion of the position on the left. That's why they are pro life, even when they want a mother to die in childbirth. That's why they call being gay a sexual preference. A large part of how they have shifted the country ever further right is by controlling the dialogue so thoroughly that it is impossible to take an even moderate progressive stance without being viewed as extremist. As soon as fake news hit the political discourse by actually literally being about conservative websites that were making up stories that never happened, it was co-opted to mean the mainstream press at large. Now no one on the left really even uses the phrase unironically to refer to the actual news that was fake leading into the election anymore. We've almost entirely stopped talking about it, because the right now owns that conversation.
Reframing the discussion to not be about the white supremacists and Nazis, but whether or not the left might be just as bad, is the same tactic that's worked for them for decades. At this point, what Antifa is in America is largely being defined by the right and their response to it, no matter the actual actions.