If you believe in conspiracy theories, anyone who disputes your ideas becomes another sinister piece in the plot.

Mundane daily life becomes magnified into a battle with the forces of evil, who are trying to destroy anyone who knows the truth.

Believers tend to think critics trying to debunk such theories are allied with the conspirators.

In the extreme, conspiracy theories can be used to legitimize violence by righteous believers who are an embattled minority or to scapegoat immigrants.

Even if they don’t result in violence, conspiracy theories can affect a large number of people by creating an atmosphere of paranoia, distrust and disbelief.

The holy trinity of anti-government conspiracy theories are gun confiscation, martial law and concentration camps, which substantially motivated Richard Poplawski, the Pittsburgh man who killed three officers called to his home by his mother in 2009.

Other examples captured their share of headlines.

James von Brunn, murdered a museum guard in June 2009 at the U.S. Holocaust Memorial Museum out of his belief Jews controlled the world.

Joseph Stack committed suicide in February in Austin by flying his small airplane into an IRS building. The ensuing inferno also claimed the life of an employee inside.

Stack, who disputed the IRS’s right to tax U.S. citizens, feared government “thugs and plunderers” were destroying his country.

In West Memphis, Ark., Jerry and Joseph Kane shot two police officers to death after being pulled over. Two more were badly wounded before they were fatally shot themselves. They traveled the country giving seminars that supposedly enabled people to avoid home foreclosure.

The fall Intelligence Report published by the Southern Poverty Law Center provides a fascinating and comprehensive overview of conspiracy ideology at a time when even satirists such as Jon Stewart and Stephen Colbert are urging America to “take it down a notch” with their Oct. 30 rival rallies on the National Mall in apparent response to Glenn Beck and the Tea Party.

Stewart’s “The Rally to Restore Sanity” was announced Sept. 16.

His event, Stewart said, is designed to attract the “70 to 80 percent of Americans who have allowed the national political discourse to become hijacked by an extremist minority of 15 percent or 20 percent of the country.”

This neglected majority, Stewart said, has been drowned out because its members have “s—t to do,” such as holding down jobs that do not include bloviating on cable television or parroting a party or corporate line for money.

Colbert immediately retaliated with his “March to Keep Fear Alive.”

As usual, these two capable comedians, even though their ratings don’t match Daniel Tosh or “South Park,” wield comedy as a scalpel to make tolerable things which aren’t really laughing matters.

The same year the Beatles hit these shores, Richard Hofstadter penned his famous essay, “The Paranoid Style in American Politics.”

At different points in American history we have been warned about imaginary threats posed by Catholics, Mormons, Jews, American Communists, Freemasons, bankers and U.S. government officials and agencies.

The last two years have seen a major resurgence, particularly the anti-government “patriot” movement with its collection of conspiracy theories implicating the federal government.

Fanning the revival was the 2008 election of President Barack Obama, whom patriots characterize as foreign-born and sent by the New World Order to destroy American sovereignty and to institute one-world socialist government.

A narrative that used to be confined to the fringes has been brought into our living rooms not just by conservative cable news hosts such as Glenn Beck of Fox News, but by Lou Dobbs, formerly of CNN.

This summer we were treated to oil conspiracy theories to keep the fear stoked — and not just from the lunatic fringe, but more to the middle of what Sarah Palin likes to call the “lamestream” media.

Radio commentator Rush Limbaugh suggested “hard-core environmentalist wackos” opposed to an energy bill that would boost offshore drilling may have been responsible for the April 20 explosion on a deep-water oil rig caused countless millions of gallons of oil to spew into the Gulf of Mexico.

“What better way to head off more oil drilling and nuclear plants than blowing up a rig?” Limbaugh asked.

Dana Perino, former spokeswoman for President George W. Bush, also floated the sabotage notion on Fox News.

Besides paranoia peddled about Obama’s birth certificate, I had never heard about the possibility that AmeriCorps was a front for a “domestic army” or that FEMA would administer  concentration camps.

The John Birch Society, which years ago quit sending us its newspaper, used to promote conspiracy theories such as President Eisenhower was a communist agent.

I hadn’t expected them to go away, but I was surprised at co-sponsorship of the Conservative Political Action Conference, an annual pow wow of leading conservatives and Republican Party figures, attended by Washington Post columnist George Will, former GOP presidential candidate Mike Huckabee and Republican House Minority Leader John Boehner of Ohio.

One popular conspiracy theory is that the Sept. 1, 2001, terror attacks on New York City and Washington, D.C., were a government plot — an inside job.

Not well-trained Al Qaeda operatives flying planes into landmarks.

World Trade Center buildings were destroyed by controlled demolitions, so their argument goes, and that one missile brought down United Airlines 93 in Pennsylvania while another hit the Pentagon.

The far left also bought into this one because it helped justify a state of perpetual war.

The far right saw 9/11 as the “crisis trigger” for the government to finally institute a police state.

In keeping with the “New World Order-controlled corporatist-Jewish media” denying the truth, a statement by  the Israeli Foreign Ministry that some “4,000 Israelis” happened to be in New York and Washington the Tuesday of the attacks, when unfounded rumors circle the globe at warp speed by the Internet, the anti-Semitic 9/11 conspiracy makes it 4,000 Israelis and Jews did not show up  for work at the World Trade Center.

Ironically, when the media do mention 9/11 claims, it is pounced on as evidence of a conspiracy within a conspiracy, such as former White House official Van Jones signing a petition calling for investigation of such allegations.

Scholars say the far right is fertile ground for conspiracy theories because they need an explanation for continued lack of power and success, so our political leaders become merely puppets, front men for the behind-the-scenes cabal really holding power.

Conspiracies figure prominently in our popular culture, from Dan Brown novels and “The X-Files” to any number of films and our continuing fascination with the JFK assassination.

I enjoy the Paul McCartney death hoax as much as anyone, but have enough logic left to know you can’t howl that the Washington bureaucracy is too inept to organize a one-car funeral, yet believe it capable of pulling off a plot as complex as 9/11.

As the Oklahoma City bombing reminds us, the greatest danger is not some government boogeyman, but when those alienated from the political process choose violence over the ballot box.

John Eby is Daily News managing editor. E-mail him at john.eby@leaderpub.com.