I am not going to be the authority on this, but I have spent some time looking at the civil rights movement. The confusion I find in most discussions about King is that white liberals always talk about nonviolence as if it was a principle, when in fact it seems to be a strategy. The difference is crucial: nonviolence as a principle means violence is never OK, while nonviolence as a strategy means that violence becomes an option when a nonviolent strategy is no longer effective.
King had very little choice but to employ a strategy of nonviolence: had he not, the white power structure in the south would have annihilated his movement before it had even gained the smallest of footholds, and it would have done so with the overwhelming support of the white population of the US. It is hard to believe that King would have stood strong through the violence the movement suffered had there been another choice.
I also believe that he had to be aware of the currency afforded him as a "reasonable alternative" to the more militant positions staked out by Malcolm, the Nation of Islam, and the Panthers. The white establishment may not have wanted to deal with King, but they wanted to deal with Elijah Muhammad, Huey Newton, Bobby Seale, or Malcolm X even less. And, with the promise of violent insurrection on the table, the liberal establishment obviously chose the nonviolent spokesman as the most reasonable negotiation partner. The degree to which King profited from the more militant positions of his peers should be clear . . . and it should be equally clear that, without the option of violent insurrection, the principle of nonviolence would be impotent.
So, as you liberals share your "Resist" memes on facebook, please take the time to consider what "Resist" really means. No rational person has violence as a first option, but neither would a rational person take violence off the table . . . "by any means necessary", as Malcolm famously said. Without Malcolm and his militant peers, we have no Martin Luther King Day today.
Oh, and while we're at it, lose that fucking poster with the Muslim woman wearing a star-spangled hijab. It was created by a white man, and it's really fucking insulting. It's clueless and white. Thanks for your cooperation.
“The great majority of Americans… are uneasy with injustice but unwilling yet to pay a significant price to eradicate it.” - Martin Luther King, Jr.