Was he a great man? He certainly showed great courage, commitment to his cause, insistence on nonviolence, strong political and leadership skills, patriotism, and became a highly eloquent spokesman for civil rights. "I Have a Dream" is one of the great speeches in the English language. King's "Letter from a Birmingham Jail" more than equals any Thoreau or Gandhi writings, and is not something that today's civil rights leaders, such as they are, could match, nor could the typical graduate of almost any university in the world today. (The letter's pacing, erudition, and, above all, the surgical preciseness with which it takes down opposing arguments bring to mind General Sherman's letter to the Mayor of Atlanta.) King's life made a difference to millions of people. The answer, therefore, to this paragraph's question is yes, he was a great man.
That said, serious problems exist with some of the narrative spun about King, in particular, and the civil rights struggle, in general. Part of the problem, of course, is that King died young, enabling others, as happened with the two Kennedy brothers, to fill in the rest of the story, and use it to further certain political agendas. King died short of his fortieth birthday; had he lived longer, presumably, he would have evolved and, possibly, become a very different man than he was when he died--we will never know. What we do know is that the Democratic Party and their "progressive" media and education machines have rewritten the history of the civil rights struggle. This was driven home to me some years ago while visiting a college campus. The students assumed King was a Democrat, and the segregationists confronting the peaceful marchers, and using fire hoses, snarling police dogs, and truncheons, and wearing white hoods were Republicans. They assume a Republican killed King--today's college kids probably believe the Tea Party had him killed. That the exact opposite is true, shocks many. King came from a staunchly Republican family--his father, a prominent leader in his own right--openly endorsed Richard Nixon against JFK in the 1960 presidential election.
The Democrats had a one-party lock on the South. The party of slave owners and secessionists, had become the party of Jim Crow, school segregation, anti-miscegenation laws, poll taxes, and on and on. Many Americans, not to mention foreigners, do not realize not only that the Republican party was formed in opposition to slavery, and that Lincoln was a Republican, but that the famous Supreme Court Chief Justice Earl Warren, whose rulings dismantled the legal basis for segregation and put serious limitations on the power of police, was a former Republican Governor of California. It was, furthermore, war hero and Republican President Dwight Eisenhower who sent troops to Arkansas to enforce court-ordered desegregation at Little Rock Central High School. Congressional Republicans were the main supporters of civil rights legislation; their votes ensured passage of the Civil Rights Act of 1964, over the opposition of a significant bloc of Democrats--let us also not forget that Congressional Democrats for years blocked Republican efforts to pass federal anti-lynching legislation. All this, of course, is history, but an important chunk of American history that is being lost, distorted, or otherwise flushed down the memory sewer--along with the fact that anti-leftist J. Edgar Hoover proved the most formidable foe of the Ku Klux Klan (KKK), an organization founded and staffed by Democrats, such as long-time Democratic Senator Robert Byrd.
Before getting back to King, let's address another issue that has been badly distorted and become something of a meme among the quasi-literate left, to wit, the idea that the parties have "switched places." This is something I have heard from some lefties who, knowing the true history of the Democratic and Republican Parties when it comes to race and civil rights, try to argue that that was then, and this is now. Since FDR or so, they argue, the Democratic and the Republican Parties "switched" places on the race issue, with Republicans taking the role of protecting white privilege and keeping minorities, especially blacks, down.
Back to King and the civil rights movement. By the time of his death, King was losing control over the movement. It was fragmenting. King's vision of a nonviolent effort was under assault by increasingly violent and radical elements. The message of non-violence and concentration on individual liberty was losing attraction. The thirty-nine-year-old King seemed old, thundering out a message from another time. A new generation of black activists, inspired by the increasingly confrontational and violent atmosphere in the country were challenging King for the spotlight. They found allies in violence in the largely white anti-Vietnam War movement.
All these factors had taken a toll on King; he aged dramatically in appearance, and had begun talking about issues not directly related to the civil rights struggle, e.g., the Middle East, Vietnam. Had he lived longer, I suspect we would have seen King becoming increasingly radicalized, pushed leftward as he sought to retain control of his movement--but, as noted before, we will never know.
In sum, he was a great man with a great vision. His successors, many of them frauds of the first rank, largely have not been faithful to that vision of liberty and color-blindness, and we all have suffered for it.