You then told two Facebook friends, and they told two Facebook friends, and so on and so forth, until all of the land was wallpapered in King's words of tolerance and wisdom. But did anyone actually stop to wonder if he actually said them? Someone did — and the answer is yes, and no.
First off, here's the quote you couldn't escape today, no matter how hard you tried:
"I mourn the loss of thousands of precious lives, but I will not rejoice in the death of one, not even an enemy. Returning hate for hate multiplies hate, adding deeper darkness to a night already devoid of stars. Darkness cannot drive out darkness: only light can do that. Hate cannot drive out hate: only love can do that." - Martin Luther King, Jr.
The consensus is that the first sentence, which circulated on its own on Twitter, was completely fabricated. What "thousands of precious lives" could King have been referring to, after all? The rest of the quote, however, is legit, and comes from King's 1963 book, Strength to Love. (Here's the page in Google Books.)
So the sentiment is authentically King's, but the part that elegantly links it to the Bin Laden case is fabricated. That information may not sway you a whole lot from your position, but at least let's get the attribution right.
UPDATE: It turns out the Mark Twain quote being tossed around by the other side, "I have never killed a man, but I have read many obituaries with great pleasure," was actually said by Clarence Darrow.
Can't anyone get a Bin Laden-appropriate quote right?