That quote could be [mis]used to defend any movement, but I don't recall MLK leading people in helmets, carrying shields, to violently confront police, without even making a clear statement of what they want.
MLK was very clear about what he meant by "justice", never tried to hide his identity, and didn't respond with violence.
"Antifa", on the other hand, aren't even honest about what they want. They call themselves anti-fascist, but they are anarchists, who dishonestly label any authority "fascist".
Anarchists of that sort are only such until they acquire structural power, then they immediately become the new, organized, violently oppressive authoritarian power. It's why Antifa so resembles the fascism they claim to oppose. That exact switch happened repeatedly across the 20th century. An organized anarchist movement is something close to an oxymoron, a facade at best, for people lusting for the power to implement their own vision of how things should be (while using that particular appeal to lure followers). The people that were responsible for installing Lenin's famines and ultimately Stalin, would of course tell you they also meant well (akin to someone claiming they mean you no harm while they break your skull).
The current American Antifa movement sprung up in direct confrontation to a government that was intent on violating every norm of democratic governance, and forcing through regulations and laws that were borderline fascist.
Trump's America absolutely was heading in a fascist direction by the strict definition of the term ("a political philosophy, movement, or regime that exalts nation and often race above the individual and that stands for a centralized autocratic government headed by a dictatorial leader, severe economic and social regimentation, and forcible suppression of opposition").
While there is no one single organized Antifa leadership or central planning, the participants were generally united by a truly genuine goal of resistance to fascism.
And violence only broke out when instigated by the state forces, bolstered by the knowledge that local, state, and federal governments are in support of them.
I thought we were talking about "an antifa vs police standoff in Berlin" 15 years ago.
But if you insist on talking about America, let me cite a recent example of Antifa dishonestly labeling anything they oppose "fascist".
Antifa rioters attacked a protest against vaccine mandates yesterday in Los Angeles. They sprayed mace on the protestors and one protestor was stabbed. They claimed the protestors were fascists and billed their response as "no safe space for fascists".
However anyone may feel about vaccine mandates, I challenge them to justify calling opposition to vaccine mandates "fascist".
The really troubling thing about Antifa is that because they label everything they oppose "fascist", they feel justified using any measure to oppose it, like spraying mace and stabbing people.
I find your comment misleading, with your article references doing the opposite of supporting your comment, especially from the latimes article.
In the latimes article, it seemed to me the anti-vaccination group was doing the attacking - also the article does not mention antifa, the only "anti" it mentions is the anti-vaccination group, who seem violently oriented in that article.
The nbc article does mention a group against fascism, but the attacking again seems to come from the anti-vax group.
So I don't see these reports as against antifa, I only see the articles supporting the idea that anti-vaxers are prone to violence, at least in this incidence.
MLK was very clear about what he meant by "justice", never tried to hide his identity, and didn't respond with violence.
"Antifa", on the other hand, aren't even honest about what they want. They call themselves anti-fascist, but they are anarchists, who dishonestly label any authority "fascist".