Progressives want progress, but toward what?
Progress as defined by MLK may be good. But what of the "progress" defined by the KKK? Not so good.
If you take morally neutral progressivism to its logical end, then progress can only be defined by power, which means that anyone—from Pelosi to Pol Pot, Reid to Robespierre, Olbermann to Obama, or even Huxley to Hitler—can claim to be the end-all and be-all of what it means to "progress."
Martin Luther King Jr. himself told us in his "Letter from Birmingham Jail" that only the higher standard of objective Justice justifies the pursuit of what is Just. He knew that God's measuring rod of righteousness was the only winning argument against man's self-righteous, self-referential, self-refuting, self-centered wrongs. He understood that God was God and that Bull Connor was not, but he likewise knew that neither was he nor was Malcolm X.
The Left thinks that when they look in the mirror they see a kind and gentle face somewhat akin to Mary Shelley's innocent young Frankenstein, a self-creation with all the sinless potential to "progress" toward utopian "goodness." They fail to see that what is really looking back at them is Robert Louis Stevenson's Mr. Hyde—someone who is sinful and broken beyond control, someone who is selfish beyond the reach of social engineering, someone we should fear, someone who cannot be redeemed by self-defined and self-centered progress, but only by selfless submission to the laws of nature and nature's God.