I actually looked up the speech last year when I heard people were making this argument, and here's the part they're cherry-picking from, where MLK says he thinks riots will only hamper the Civil Rights Movement.
"Now, I wanted to say something about the fact that we have lived over these last two or three summers with agony and we have seen our cities going up in flames. And I would be the first to say that I am still committed to militant, powerful, massive, non-violence as the most potent weapon in grappling with the problem from a direct action point of view. I'm absolutely convinced that a riot merely intensifies the fears of the white community while relieving the guilt. And I feel that we must always work with an effective, powerful weapon and method that brings about tangible results. But it is not enough for me to stand before you tonight and condemn riots. It would be morally irresponsible for me to do that without, at the same time, condemning the contingent, intolerable conditions that exist in our society. These conditions are the things that cause individuals to feel that they have no other alternative than to engage in violent rebellions to get attention. And I must say tonight that a riot is the language of the unheard. And what is it America has failed to hear? It has failed to hear that the plight of the negro poor has worsened over the last twelve or fifteen years. It has failed to hear that the promises of freedom and justice have not been met. And it has failed to hear that large segments of white society are more concerned about tranquility and the status quo than about justice and humanity."
It's almost like people didn't care what he actually said, and are only using out of context quotes that suit their own political beliefs.
