A “moonbat” is an epthet used against the politically liberal left wing, similar to the words “lunatic” and “batty.”  Perry de Haviland of the libertarian blog Samizdata.net coined the political use of the term in 2002, although de Haviland has claimed use of the term since 1999. An early form was “barking moonbat,” similar to dogs howling at the moon. De Haviland says that the term “moonbat” does not refer to British enviuronmental and political activist George Monbiot.
   
An activity of moonbats might be “moonbatty,” and a collection of moonbats is sometimes called a “moonbattery.” California politician Jerry Brown was called ‘Governor Moonbeam” in 1979, but “moonbeam” never entered the lexicon to refer to any other person.
 
A person who opposes the “moonbat” philosophy is a “countermoonbat.” A moonbat is frequently crazy or “moonbatty” (moonbat + batty).
     
 
Wikipedia: Moonbat
Moonbat is a term used in United States politics as a political epithet referring to social liberals or leftists.
   
Etymology
According to an article by self-described New York Times “language maven” William Safire, the term was first used by science fiction author Robert A. Heinlein in 1947. Heinlein used the term in a 1947 short story, “Space Jockey,” as the name of the third stage of a rocket bound for the moon. Descriptions of bat-like people on the moon were part of the 1835 Great Moon Hoax. One explanation for the current political use is that the term was derived from the name of liberal author George Monbiot.
 
Examples of usage
. According to William Safire, “The prevailing put-down of right-wing bloggers is winggnuts;  this has recently been countered by the vilification of left-wing partisans who use the Web as moonbats...”
. On March 14, 2000 Jonah Goldberg’s National Review Online column “Our, *ahem*, FAQ Welcome New Readers” contained the following: “Alas, because Goldberg watches Baywatch everyday and can name the main characters in almost every Marvel comic book from 1976 to 1986, he occasionally makes errors. Far more often, he simply writes things that make readers say, “Is this guy higher than a moonbat?”“
   
Glossary - Samizdata.net
Barking moonbat
noun. Someone on the extreme edge of whatever their -ism happens to be.
(coined by Perry de Havilland)
 
Usage:“Definition of a ‘barking moonbat’: someone who sacrifices sanity for the sake of consistency”
-Adriana Cronin
 
Although the term (often rendered simply as “Moonbat”) is very popular with conservative and libertarian bloggers who appropriately use it to describe the Chomskyite Left, it was always intended as a much more ecumenical epithet and has been correctly used to describe certain paleo-conservative and paleo-libertarians views. (also see “idiotarian”).
 
Note: Contrary to some speculation and entries on Wikipedia (which constantly change to reflect the prevailing wind of the day it seems), Perry de Havilland has stated it was was not originally a play on the last name of George Monbiot, a columnist for The Guardian, as he was using the term long before he met or had even heard of Mr. Monbiot.
 
Kossary - dKosopedia
Moonbat
Derogatory right-wing blogger term for liberals, denoting supposed detachment from reality. Hardcore offenders may be “barking moonbats”. Frequently used to belittle liberals by portraying them as quaint, outmoded, silly, or comical - a favored tactic of the triumphalist Right.
       
Urban Dictionary
moonbat 
An unthinking or insane leftist—in other words, most modern leftists.
 
Moonbat can also be used as an adjective, e.g. a moonbat professor. According to the Wikipedia entry for moonbat, the word was coined in 2002 by the Editor of Samizdata, Perry de Havilland, and was a variation on the name of radical British activist and columnist George Monbiot.
 
Originally, the term “moonbat” was intended to be more politically neutral, and described wackos on the left and the right, but it quickly acquired its current usage of being applied almost exclusively to those on the left.
 
The term also references the moon much in the same way that “lunatic” refers to the insanity-causing powers of the full moon (luna = moon). Bloggers occasionally analyze the behavior patterns of various moonbat “species” as if they were actual animals, and even give them satirical Linnaean taxonomical names, such as “moonbattus berkeleyensis”.
 
The entry in the Samizdata glossary indicates that Perry originally coined the full phrase “barking moonbat”; apparently “moonbat” is just a subsequent shortened version of “barking moonbat,” rather than being a pre-existing term that was lengthened to barking moonbat.
 
Worker #1 “Did you see those moonbats on the news staging another one of their useless protests?”
Worker #2 “Yeah, all eight of them.”
Worker #1 “Man, they need to get real jobs.”
by Garlic M. May 3, 2007
   
Wikipedia: George Monbiot
George Joshua Richard Monbiot (born 27 January 1963) is a British writer, known for his environmental and political activism. He writes a weekly column for The Guardian, and is the author of a number of books, including Captive State: The Corporate Takeover of Britain (2000) and Bring on the Apocalypse: Six Arguments for Global Justice (2008). He is the founder of The Land is Ours campaign, which campaigns peacefully for the right of access to the countryside and its resources in the UK.
 
The Independent writes that Monbiot is the acceptable face of green activism, in that he “eats meat, doesn’t take to the trees, and won’t swear at policemen.”
   
11 October 1979, New York (NY) Times, “Gov. Brown Brings His Campaign to New York City” by Wayne King, pg. A18:
Gov. Edmund G. Brown Jr. of California yesterday made his first serious incursion of the campaign season into New York City on his quest for the Presidency, laughing away the characterization of him as ‘Governor Moonbeam” and proposing that oil companies be put under Federal control.
 
Samizdata.net
March 21, 2002
Thursday
Harry Browne gets blogged over the head by Foxy Andrea
Perry de Havilland (London)  North American affairs • Opinions on liberty
Andrea Harris is the Fox News guest blogger and showcases former US Libertarian Party candidate Harry Browne’s wit and wisdom.
 
So will people please just read this and then stop asking me why I keep saying that Browne and his Libertarian Party do not define libertarianism in the USA. Guys, face facts… as long as you have a barking moonbat like Browne who thinks a libertarian society could survive contact with reality in the manner he advocates, the vast majority of US libertarians will continue to either vote Republican or if they cannot stand that, just not vote at all.
   
Samizdata.net
May 05, 2002
Sunday
Samizdata slogan of the day
Samizdata Illuminatus (Arkham, Massachusetts)  Slogans/quotations
Definition of a ‘barking moonbat’: someone who sacrifices sanity for the sake of consistency.
- Adriana Cronin
         
The Bear Pit Politicial Forum
Boon Mee
Jul 20 2004, 02:18 PM
Yep, not a single response from the Barking Moonbats!
 
New York (NY) Times
On Language
Moon Bats & Wing Nuts
By WILLIAM SAFIRE
Published: September 3, 2006
(...)
The online source reports that “the phrase was popularized in 2002 by Perry de Havilland of Samizdata.net, a libertarian blog. . .originally rendered as ‘Barking Moonbat,’ suggesting that certain issues seem to trigger a reflexive response from some people much like wolves howl at the moon.”
 
Reached at the blog he founded, de Havilland says he began using the term in 1999, during his “preblogging days.” He holds that it is nonideological: “Although the term has become beloved by conservatives to describe people on the left, and certainly I think the quintessential moonbat is Noam Chomsky, it is really quite an ‘ecumenical’ term of abuse for dogmatists of any ilk — left, right or libertarian.”
(...)
In his 1947 short story “Space Jockey,” he (Robert Heinlein—ed.) named the third stage of a rocket to the moon the Moonbat, and in another story a year later, “The Black Pits of Luna,” one Heinlein character was the scoutmaster of the Moonbat Patrol.