Martin Luther King, Jr. (1929- 1968) gave the sermon “Loving Your Enemies” in Ebenezer Baptist Church on Sunday morning, August 12, 1962:
 
“The process of returning hate for hate only multiplies the existence of hate in the universe. It adds deeper darkness to a night already devoid of stars. Darkness cannot drive out darkness; only light can do that. More hate cannot drive out hate, only love can do that. Along the way of life someone must have sense enough to cut off the chain of hate and evil. Someone must meet hate with love; someone must meet physical force with soul force.”
 
The sermon was reprinted in King’s book, Strength to Love (1963). King’s statement that “returning hate for hate multiplies hate” was used by at least one opinion writer on September 18, 2001, referring to the events of September 11, 2001.
 
Osama bin Laden (the terrorist involved in the September 11th events) was killed by U.S. forces on May 1, 2011. Jessica Dovey, an English teacher in Japan, wrote on her Facebook page an original line, followed by King’s words:
 
“I will 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.’”
 
Dovey’s line went viral on the Internet, incorrectly attributed to Dr. King. The correct story of the quotation made national news.
   
 
Wikipedia: Martin Luther King, Jr.
Martin Luther King, Jr. (January 15, 1929 – April 4, 1968) was an American clergyman, activist, and prominent leader in the African American civil rights movement. He is best known for being an iconic figure in the advancement of civil rights in the United States and around the world, using nonviolent methods following the teachings of Mahatma Gandhi. King is often presented as a heroic leader in the history of modern American liberalism.
 
A Baptist minister, King became a civil rights activist early in his career. He led the 1955 Montgomery Bus Boycott and helped found the Southern Christian Leadership Conference in 1957, serving as its first president. King’s efforts led to the 1963 March on Washington, where King delivered his “I Have a Dream” speech. There, he expanded American values to include the vision of a color blind society, and established his reputation as one of the greatest orators in American history.
 
In 1964, King became the youngest person to receive the Nobel Peace Prize for his work to end racial segregation and racial discrimination through civil disobedience and other nonviolent means. By the time of his death in 1968, he had refocused his efforts on ending poverty and stopping the Vietnam War.
 
King was assassinated on April 4, 1968, in Memphis, Tennessee. He was posthumously awarded the Presidential Medal of Freedom in 1977 and Congressional Gold Medal in 2004; Martin Luther King, Jr. Day was established as a U.S. federal holiday in 1986.
 
13 September 1962, Kingsport (TN) News, pg. 4, col. 6:
“Loving Your Enemies”
(Just what is the policy of non-violence upon which Martin Luther King has built his leadership of Negro integration forces? Dr. King explains it himself in this fourth article of a series.)
By BOB CONSIDINE
ATLANTA—Early last month, while confined to a primitive jail in Albany, Ga., Dr. Martin Luther King wrote a sermon to be delivered whenever the course of events would again make him a free man. he titled it “Loving Your Enemies.”
 
Dr. King returned to Atlanta shortly after his release, hand-written sermon in his briefcase, and delivered it to a capacity congregation at Ebenezer Baptist Church on Sunday morning, Aug. 12.
 
Excerpts from the sermon are herewith printed for the first time:
(...)
“The process of returning hate for hate only multiplies the existence of hate in the universe. It adds deeper darkness to a night already devoid of stars. Darkness cannot drive out darkness; only light can do that. More hate cannot drive out hate, only love can do that. Along the way of life someone must have sense enough to cut off the chain of hate and evil. Someone must meet hate with love; someone must meet physical force with soul force.”   
 
Google Books
Strength to Love
By Martin Luther King, Jr.
Philadelphia, PA: Fortress Press
1981, ©1963.
Pg. 52:
Let us move now from the practical how to the theoretical why: Why should we love our enemies? The first reason is fairly (Pg. 53—ed.) obvious. 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. Hate multiplies hate, violence multiplies violence and toughness multiples toughness in a descending spiral of destruction.
 
Google News Archive
18 September 2001, Rome (GA) News-Tribune, Our World, pg. 4, col. 3:
Piling up bodies solves nothing
By MATTHEW ROTHSCHILD, Guest Colmunist
I DO NOT SHARE the blood lust in the Congress, in the media and among the populace. I do not believe the United States should go to war.
 
Horrified as I am by the heinous attacks on Sept. 11, I do not favor massive retaliation.
 
Even as my heart goes out to the families of all those victims, I cannot bring myself to call for more bloodshed.
 
“Returning hate for hate multiplies hate,” the Rev. Martin Luther King Jr. wrote in 1963. “Violence multiplies violence, and toughness multiplies toughness in a descending spiral of destruction.”
 
The Atlantic
Anatomy of a Fake Quotation
By Megan McArdle
May 3 2011, 10:13 AM ET
(...)
Here’s the quote as most people on Facebook saw it:
 
I will 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.
 
Everything except the first sentence is found in King’s book, Strength to Love, and seems to have been said originally in a 1957 sermon he gave on loving your enemies.  Unlike the first quotation, it does sound like King, and it was easy to assume that the whole thing came from him.
 
So how did they get mixed together?
 
Thanks to Jessica Dovey, a Facebook user, that’s how.  And contrary to my initial assumption, it wasn’t malicious.  Ms. Dovey, a 24-year old Penn State graduate who now teaches English to middle schoolers in Kobe, Japan, posted a very timely and moving thought on her Facebook status, and then followed it up with the Martin Luther King Jr. quote. 
 
I will 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.” MLK Jr.
 
Christian Science Monitor
How Osama bin Laden’s death sparked a fake Martin Luther King quote
A Facebook user’s message about Osama bin Laden’s death quickly mutated into a misattributed quote by Martin Luther King, showing us all how quickly the Internet can generate an urban legend.
By Eoin O’Carroll, CSMonitor.com / May 3, 2011
If you were online Monday, there’s a decent chance you spotted this quote:
 
“I mourn the loss of thousands of precious lives, but I will not rejoice in the death of one, not even an enemy.”—Martin Luther King, Jr.
(...)
Just one problem: There’s no evidence that Martin Luther King ever said such a thing.
 
By Tuesday morning, the blogosphere was starting to catch on. One of the first was Salon’s Drew Grant, who shot from the hip and grazed an innocent Las Vegas magician with a post headlined, “Why did Penn Jillette create a fake Martin Luther King Jr. quote yesterday?”
(...)
The first sentence is Ms. Dovey’s own, followed by a quotation from King’s 1963 book, “Strength to Love.” At some point along the way, the quote marks vanished, and Dovey’s words got mixed up with King’s. Subsequently, the quote was shortened, leaving only Dovey’s line, now attributed to the civil rights leader.
 
The Last Word Blog
Fake MLK quote from bin Laden’s death
By nick ramsey -  Tue May 3, 2011 3:35 PM EDT.
(...)
You may still be saying to yourself, “It does sound like something Martin Luther King, Jr. would have said.” Indeed, I agree. It does. But there’s a reason for that. The sentiment in this remark also appears in a certain text that Dr. King knew rather well.
 
Say to them, ‘As surely as I live, declares the Sovereign Lord, I take no pleasure in the death of the wicked, but rather that they turn from their ways and live. Turn! Turn from your evil ways! Why will you die, people of Israel?’
- Ezekiel 33:11
 
The Atlantic
The (Shy) Woman Whose Words Accidentally Became Martin Luther King’s
By Alexis Madrigal
May 3 2011, 7:19 PM ET
Jessica Dovey did not intend to become the epicenter of an Internet-wide discussion about the nature of quotation, attribution, and Osama bin Laden. Yet that’s exactly what happened when Dovey’s Facebook-status sentiment—“I will mourn the loss of thousands of precious lives, but I will not rejoice in the death of one, not even an enemy”—became entangled with a Martin Luther King, Jr. quote she also posted. Within a day and through no fault of her own, Dovey’s words had gone viral, misattributed to King.
(...)
Did you know the King quote before you used it?
That Martin Luther King quote is one of my favorite, favorite, favorite quotes. I knew it before I posted it, but it definitely felt appropriate at the moment. He said it way better than I could ever say it.
 
When did you know that your words had taken off and gone viral?
I didn’t actually know until about 10 hours ago. Someone posted on the original comments thread and said, “Well, it’s gone viral.” I said “No, way.” So I Googled what I said and, it brought up Martin Luther King Jr. I thought, “This is ridiculous. This is not his quote.” And I was like, “Oh, no.”