“Drinking the Kool-Aid” means to follow a leader or a philosophy without critical examination. Kool-Aid is a flavored drink mix that was invented in 1927. “Drinking the Kool-Aid” refers to the November 1978 massacre of over 900 people at the officially named Peoples Temple Agricultural Project (Jonestown) in northwestern Guyana. Jonestown’s founder, the spiritual leader Jim Jones, was being investigated by a member of Congress (who was assassinated in the tragedy). Jones then directed his followers to commit suicide by giving them Flavor Aid (not Kool-Aid, but a rival product) laced with Valium, chloral hydrate, cyanide, and Phenergan. Although the phrase “drinking the Kool-Aid” often refers to blind following, many members of the Peoples Temple were held in Jonestown at gunpoint, against their free will to leave.
 
The phrase “drink(ing) the Kool-Aid” has been cited in print since at least 1981, but citations within ten years of the 1978 tragedy are rare. The phrase began to be used frequently in the 1990s. “Drinking the Kool-Aid” has been used in politics, usually to warn against the cult-like blind following of a political interest group, a political party or a politician.
   
 
Wikipedia: Kool-Aid   
Kool-Aid is a brand of flavored drink mix owned by the Kraft Foods Company, and manufactured by its Mexican subsidiary.
 
Invention and production
Kool-Aid was invented by Edwin Perkins and his wife Kitty in Hastings, Nebraska, United States. All of his experiments took place in his mother’s kitchen. Its predecessor was a liquid concentrate called Fruit Smack. To reduce shipping costs, in 1927, Perkins discovered a way to remove the liquid from Fruit Smack, leaving only a powder. This powder was named Kool-Aid. Perkins moved his production to Chicago in 1931 and Kool-Aid was sold to General Foods in 1953.
(...)
In popular culture
. “Drinking the Kool-Aid” refers to the 1978 Jonestown Massacre; the phrase suggests that one has mindlessly adopted the dogma of a group or leader without fully understanding the ramifications or implications: at Jonestown, Jim Jones’s followers followed him to the end: after visiting Congressman Leo Ryan was shot at the airstrip, all the Peoples Temple members drank from a metal vat containing a mixture of “Kool Aid”, Cyanide, and prescription drugs Valium, Phenergan, and chloral hydrate. The poison at Jonestown, however, was mixed not with Kool-Aid but a similar product, Flavor Aid.
   
Wikipedia: Drinking the Kool-Aid
“Drinking the Kool-Aid” is a phrase and metaphor, used in the United States and Canada, that means to become a firm believer in something, to accept an argument or philosophy wholeheartedly or blindly without critical examination. The term originated with the November 1978 Jonestown Massacre, where members of the Peoples Temple were said to have committed suicide by drinking Kool-Aid laced with cyanide.
 
Evidence gathered at the Jonestown site after the incident indicated that Flavor Aid (a similar powdered drink mix), rather than Kool-Aid, was used in the massacre. Some survivors of the incident object to the link between blind faith and the People’s Temple implied by the phrase, since some victims were murdered rather than being convinced or forced to commit suicide.
 
Objections notwithstanding, the phrase is commonly used in a variety of contexts to describe blind, uncritical acceptance or following, generally in a derogatory sense.
 
Wikipedia: Jonestown
Jonestown was the informal name for the Peoples Temple Agricultural Project, an intentional community in northwestern Guyana formed by the Peoples Temple, a cult led by Jim Jones. It became internationally notorious when, on November 18, 1978, 918 people died in the settlement as well as in a nearby airstrip and in Georgetown, Guyana’s capital. The name of the settlement became synonymous with the incidents at those locations.
 
A total of 909 Temple members died in Jonestown, all but two from apparent cyanide poisoning, in an event termed “revolutionary suicide” by Jones and some members on an audio tape of the event and in prior discussions. The poisonings in Jonestown followed the murder of five others by Temple members at a nearby Port Kaituma airstrip. The victims included Congressman Leo Ryan, the first member of Congress assassinated in the line of duty in the history of the United States. Four other Temple members died in Georgetown at Jones’s command.
 
To the extent the actions in Jonestown were viewed as a mass suicide, it is the largest such event in modern history and resulted in the largest single loss of American civilian life in a non-natural disaster until the events of September 11, 2001.
(...)
A 44-minute cassette tape (the “death tape”), recorded at least part of a meeting Jones called under the pavilion in the early evening. Before the meeting, aides prepared a metal vat with Flavor Aid, poisoned with Valium, chloral hydrate, cyanide, and Phenergan.
 
(Oxford English Dictionary)
U.S. to drink the Kool-Aid: to demonstrate unquestioning obedience or loyalty. Also to drink the —— Kool-Aid: to support —— wholeheartedly; to commit unquestioningly to ——.
1987 Washington Post 17 July a8   You don’t follow anyone blindly‥. We love Marion Barry‥. But if Marion Barry disrespects us, we will cry out‥. We will not blindly drink the Kool-Aid any longer.
1996 Time 2 Sept. 28/2   He’s like a cult leader‥. The client has to get in there, drink the Kool-Aid and look him in the eye.
2002 N.Y. Times Mag. 6 Oct. 80/3   A big reason people in this city were initially reluctant to drink the New Economy Kool-Aid was the sense that the digital revolution threatened our primacy in the national economy and culture.
   
20 February 1981, Gettysburg (PA) Times, pg. 1, col. 5:
Ginsberg Tells Of Kool
Aid Of Nuclear Power
By M. EILEEN GRAHAM
Times Correspondent
“There is something new under the sun—it’s plutonium.” a new element described by the renowned American poet Allen Ginsberg Thursday night in a Gettysburg College audience participating in the 50s Festival being held there to examine an era of contrasts and change.
(...)
“We are all being put in the place of the citizens of Jonestown, being told by our leaders to drink the Kool Aid of nuclear power,” he said, stressing his dismay at the return to right-wing politics and morality in America.
 
Google Books
The U.S. Executive Branch/PATCO job action of August 3, 1981 : its causes and ramifications
By Claude M. Schonberger
Publisher: [S.l. : s.n.]
1982
Pg. 4:
Brainwashing—The strike was caused by peer pressure, using exceedingly persuasive techniques that misled the unwary. ‘They all drank the Kool-Aid,” was the manner in which it was frequently stated.
   
Google Books
Private Eye
Issues 497-522
Pressdram
1981
Pg. 10: 
“We’d just have to drink the Kool-Aid,” said one staff member acidly.
 
Google News Archive
17 February 1982, Dubuque (IA) Telegraph-Herald, pg. 2, col. 2:
Kirkland slams Reagan plans
as “Jonestown economics”
BAL HARBOUR, Fla. (UPI)—“Jonestown economics” is how AFL-CIO President Lane Kirkland described President Reagan’s proposals to revitalize the economy.
(...)
Kirkland, in explaining his “Jonestown economics” comment to reporters, said: “It administers economic Kool-Aid to the poor, and the deprived, and the unemployed in this country.”
 
The Kool-Aid reference was to the poisoned fruit-drink mixture that hundreds of the Peoples Temple followers of the Rev. Jim Jones drank before dying at his retreat at Jonestown, Guyana in November 1978.
 
Google Books
Shooting Ourselves in the Foot
By Bernard J. O’Keefe
Boston, MA: Houghton Mifflin
1985
Pp. 178-179:
The press labeled him “the Reverend Jim Jones of the American labor movement,” referring to the mass suicides that had recently taken place in Guyana and speculated on how he had talked the members into “drinking the Kool- Aid.”
Pg. 180:
That is the question all members of American organized labor must ask: “Are we all just kicking the stool out from under ourselvews?” Other unions seem to be drinking the Kool-Aid, perhaps not as dramatically as PATCO, but just as fatally.
 
OCLC WorldCat record
Cuname, curare & cool aid : the politics that spawned and nurtured Jonestown
Author: George Jackson
Publisher: New York : G.D. Jackson Associate, ©1986.
Edition/Format:  Book : English : 1st ed
     
Google Books
New American Writing
Issues 1-3
Oink! Press
1987
Pg. 72:
Subordination is an aid to unity. Insubordination means you never drank the kool aid.
 
OCLC WorldCat record
The Jonestown massacre, aka “the kool-aid congregation”
Author: Jeffrey Adam Baxt; Dan O’Connor; Thom Zahler
Publisher: Berlin, NJ : Comic Zone Productions, ©1992.
Series: Killer cults, v. 1. 
Edition/Format:  Book : English
 
OCLC WorldCat record
Fortune Investor - AGAINST THE GRAIN - The Danger Lurking In Investor Message Boards - At their worst, financial chat rooms are the investment version of poisoned Kool-Aid
Author: Herb Greenberg
Publisher: [New York, NY, etc., Time, inc., etc.]
Edition/Format:  Article : English
Publication: Fortune. 138, no. 10, (1998): 322
Database: ArticleFirst
   
OCLC WorldCat record
Drinking the Kool-Aid - Watch the top line, say Amazon’s acolytes. Okay, it’s wavy.
Author: Mark Veverka
Publisher: Chicopee, Mass. : Dow Jones & Co., 1994-
Edition/Format:  Article : English
Publication: Barron’s. (August 02, 1999): 47
Database: ArticleFirst
   
OCLC WorldCat record
Drinking the Kool-Aid: The Cultural Transformation of a Tragedy
Author: Rebecca Moore
Publisher: University of California Press
Edition/Format:  Article : English
Publication: Nova Religio, 7, no. 2 (2003): 92-100
Database: ArticleFirst
 
OCLC WorldCat record
Drinking the Kool-Aid
Author: W Patrick Lang
Publisher: Blackwell Publishing
Edition/Format:  Article : English
Publication: Middle East Policy, 11, no. 2 (2004): 39-60
Database: ArticleFirst
 
OCLC WorldCat record
Nonfiction - NONFICTION CHRONICLE - NEVER DRANK THE KOOL-AID: Essays. By Toure
Author: Tara McKELVEY
Publisher: New York, N.Y. : New York Times Co.,
Edition/Format:  Article : English
Publication: The New York times book review. (April 09, 2006): 16
Database: ArticleFirst
 
OCLC WorldCat record
Drinking the Kool-Aid: Was the Iraq adventure doomed to fail or did the US mess it up? A new crop of books suggests the right war was fought in theory but not practice
Author: M Leonard
Edition/Format:  Article : English
Publication: PROSPECT -LONDON- PROSPECT PUBLISHING LIMITED- no. 119, (2006): 26-29
Database: British Library Serials
 
OCLC WorldCat record
Drinking the Kool-Aid : power and elite masculinities in corporate America
Author: Whit Missildine
Publisher: 2007.
Dissertation: Thesis (Ph. D.)—City University of New York, 2007.
Edition/Format:  Thesis/dissertation : Manuscript Archival Material : English
   
OCLC WorldCat record
Letter: How to drink the sub-prime kool-aid
Author: Varian H.R.
Edition/Format:  Article : English
Publication: Economists’ Voice, v5 n5 (2008 09 12):
 
OCLC WorldCat record
Don’t drink the kool-aid : Oprah, Obama and the occult
Author: Carrington Steele
Publisher: [S.l.] : Carrington Steele, 2008.
Edition/Format:  Book : English
 
OCLC WorldCat record
Drinking the Kool-Aid: The IMF and Global Hegemony
Author: J Mueller
Edition/Format:  Article : English
Publication: MIDDLE EAST CRITIQUE, 19, no. 2, (2010): 93-114
Database: British Library Serials
 
OCLC WorldCat record
Coffee, tea, or kool-aid : which party politics are you swallowing?
Author: Erin McHugh
Publisher: New York : Abrams Image, 2010.
Edition/Format:  Book : English
Summary: A humorous guide to two new, headline-grabbing political movements