The famous civil rights leader did have a great quote for today's news, but it's probably not the one you've seen.
An apparently fake Martin Luther King Jr. quotation is making the internet rounds today in the wake of Osama bin Laden's killing, probably because the passage seems tailor-made for such an event. The quotation—"I mourn the loss of thousands of precious lives, but I will not rejoice in the death of one, not even an enemy"—has been popping up in Twitter feeds around the world, and yet it's nowhere to be found in any of the extensive online records of King's famous historical speeches and writings.
From now on, when you'd like to express your displeasure with the hordes of people cheering with glee at bin Laden's slaying, try using these two perfectly acceptable, perfectly authentic writings in lieu of that bogus one (one of them is even verifiably from King):
1. "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. ... The chain reaction of evil—hate begetting hate, wars producing more wars—must be broken, or we shall be plunged into the dark abyss of annihilation." -Martin Luther King Jr., Strength to Love\n
2. "Do not rejoice when your enemies fall, and do not let your heart be glad when they stumble." -Proverbs 24:17\n
Update: It turns out that the origin of the fake MLK quote was a woman named Jessica Dovey, whose harmless Facebook update had people confused about where her words ended and King's began. The rest is internet history.