Listening again to Rev. Martin Luther King Jr.’s famous “I Have a Dream” speech, delivered 50 years ago this week in the “symbolic shadow” of Abraham Lincoln, you are reminded once again of King’s forceful, radical nature. It’s an aspect of his character that has been sandpapered down with the passage of time and with his ascension into the pantheon of great, and thus “safe,” American leaders.

This famous son of Georgia speaks of the “fierce urgency of now,” warning against “the luxury of cooling off or … the tranquilizing drug of gradualism.”

“It would be fatal for the nation to overlook the urgency of the moment,” he warns ominously. “This sweltering summer of the Negro’s legitimate discontent will not pass until there is an invigorating autumn of freedom and equality. Nineteen sixty-three is not an end, but a beginning. Those who hope that the Negro needed to blow off steam and will now be content will have a rude awakening if the nation returns to business as usual.”

And the sad truth is, the nation probably would have returned to business as usual. It took the assassination of John F. Kennedy three months later, and the emotional trauma inflicted by that tragedy, to jolt Congress into doing the right thing by passing civil rights legislation.

Much of the progress that King hoped to see someday has been accomplished in these past 50 years, and it’s important to celebrate that progress. He spoke of a dream “that one day on the red hills of Georgia, the sons of former slaves and the sons of former slave owners will be able to sit down together at the table of brotherhood,” and in many ways that has come to pass. He noted that “America has defaulted on this promissory note (of freedom and equality) insofar as her citizens of color are concerned,” but he might be a bit amazed by the fact that the president of the United States who commemorated the 50th anniversary of the March on Washington on Wednesday is a black man.

Then again, maybe he wouldn’t be amazed at all.

King drew great strength from his religious faith, from his belief that the “The arc of the moral universe is long, but it bends toward justice,”as he put it in a later speech. However, he also had a profound and abiding faith in this country and in its better instincts.

I’m always struck by his genius in framing the civil rights struggle within the context of American patriotism, as a challenge to the country to finally live up to the exalted promises of the Declaration of Independence and the Constitution that all of us are created equal, with equal access to “the unalienable rights of life, liberty, and the pursuit of happiness.”

We aren’t there yet though, not fully. As we’ve seen in debates about racial profiling by law enforcement, some still argue that it is legitimate for government authorities to judge people “by the color of their skin” not “the content of their character,” and to treat them differently on that basis.

And while the presence of Barack Obama in the Oval Office does indeed validate King’s optimism, it has also inflamed insecurity among those who have experienced Obama’s success, even subconsciously, as a threat or loss to their own standing. That sentiment — born more of fear than of hate at this point — still survives in enough people to make it profitable to pander to it.

Yet with each passing day and each passing generation, even that will fade. Like King, I have faith in this nation, its people and its founding credos, and in the fact that though “the arc of the moral universe is long, it bends toward justice.”