Since March 2009 , Wikipedia has had a variant of this smear of the Minuteman Project ("MMP") on their Vigilante entry:
The Minuteman Project has been described as vigilantes dedicated to expelling people who cross the US-Mexico border illegally.
Since that quote was added, Wikipedia has backed up its claim with two highly questionable sources, as will be described below.
First note that the same Wikipedia page gives a different treatment to other groups:
Members of neighborhood watch programs and others who use legal means of bringing people to justice are not considered vigilantes. For example, in 1979 Curtis Sliwa founded the Guardian Angels in New York City, a recognized crime fighting organization that now has chapters in many other cities.
No doubt the Guardian Angels and many non-vigilante neighborhood watch programs have been "described as vigilantes", yet those groups aren't given the same "has been described" treatment as the MMP.
Wikipedia's smear of the MMP links to two highly questionable sources.
The first highly questionable source is "New Video Appears to Show Vigilante Border Murder" from splcenter . org/blog/2007/08/13/
new-video-appears-to-show-vigilante-border-murder. As the SPLC admits on a later page at their site , the video in question was fake and the person who made it led a different organization and only "[a]t one time [doubled] as the head of Campo operations for the Minuteman Project". After the video was released, the maker of the video was banned from the MMP. There's no update in the SPLC post that Wikipedia links to indicating that the video was fake and that the MMP severed the limited ties they had to its maker. A news report confirming that the video was not real is at .
Casual readers of the Wikipedia Vigilante entry might assume that the MMP itself murdered someone, when that's not at all the case. Bear in mind that Wikipedia has been linking to the questionable SPLC post since March 2009.
The other highly questionable source is "Vigilantes Gather in Arizona" from adl . org/learn/extremism_in_the_news/
White_Supremacy/arizona_vigilantes_40705.htm. That blog post does refer to the MMP as "vigilantes" but it also makes other misleading claims. It states that the MMP was "designed by anti-immigration extremists". The MMP has taken great pains to point out that everything they did was within the law, and wanting to reduce illegal immigration isn't an "extremist" point of view: it's one held by most Americans. Further, the term "anti-immigration" implies that someone is against all forms of immigration, when that's not the case with many or most who want to reduce illegal immigration. The ADL post also makes this misleading claim:
The Minuteman Project has been advertised on various extremist Web sites. For example, an Aryan Nation Web site links to the Minuteman Project, proclaiming "a call for action on part of ALL ARYAN SOLDIERS."
The use of the word "advertised" implies that the MMP paid groups to link to them or the like despite that not being the case. An organization has no control over other groups linking to them. If an extremist group links favorably to the ADL, should we hold the ADL responsible for the statements of that extremist group? The ADL is subtly trying to mislead their readers into thinking that the MMP accepts the support of fringe groups, when that isn't the case. Further, the ADL is a contentious group, even at Wikipedia .
In summary, Wikipedia is basing their long-running smear on two very questionable sources with known biases and isn't giving one group the same treatment given other similar groups.
 The smear was first added in a form close to what it is now (Jan. 2012) by user "Zombie Hunter Smurf" at 16:42, 21 March 2009:
The Minuteman Project have beed described as vigilantes dedicated to expelling people who cross the US-Mexico border illegally.
Someone later corrected the spelling, but that sentence has linked to the two articles discussed above since it was added by that user. Previous versions of the page contained other smears of the MMP and the Minuteman Civil Defense Corps.
 The page splcenter . org/get-informed/intelligence-report/
browse-all-issues/2008/spring/the-nativists?page=0,3 describes the person who made the video:
Crooks, a retired commercial fishermen from Oregon, first set up camp in May 2006. His tiny outfit, the Mountain Minutemen, also known as the Patriot Point Posse, is one of several particularly hard-core rogue Minutemen factions operating in the rugged border region between Campo and Jacumba, Calif. At one time, Crooks was doubling as the head of Campo operations for the Minuteman Project. But his penchant for name-calling and gunplay have made him persona non grata among Minutemen leaders who court mainstream media coverage.
For example, in July 2007 Crooks distributed a chilling video that appeared to show a Mexican immigrant being hunted and killed by a Minuteman sniper using a night-vision scope. After the Intelligence Report publicized the video, Crooks told law enforcement investigators that he and another Minuteman had staged it because "[w]e're old men and we're bored." Minuteman Project leader Jim Gilchrist subsequently banned his group's members from having any contact with Crooks, and stated publicly that he would no longer provide Crooks with supplies.
 from 10news.com/news/13923784/detail.html
One Minuteman leader accused a rival Minuteman leader of videotaping the shooting of an illegal immigrant, but sheriff's deputies investigating the report Saturday said the video was fake, as did the maker of the video.
...The video, which is shot from the perspective of a gun scope, was probably staged, said Sgt. Mike Radovich of the San Diego County Sheriff's Department Campo station.
...An agent with the Border Patrol said the group may have been effective at preventing some immigrants from illegally crossing the border near his trailer, but that "they walk right by Crooks now."
"I take his videos on YouTube with a grain of salt," said the border agent.
 Various pages at Wikipedia question whether the ADL is a credible source (other pages ask the same about the SPLC). The results are mixed: