(CNN) Fake news stories emerged with jarring force during the 2016 presidential campaign, and in a dangerous episode this weekend the potency of this deceptive new way of packaging and spreading conspiracy theories showed its continued influence.

When Washington police said Sunday night that a 28-year-old man, who allegedly walked into a local pizzeria hours earlier with an assault rifle in hand, told officers he traveled from North Carolina to conduct an informal probe of something called "pizza gate," expressions of shock and worry mixed in with knowing shrugs.

The flourishes of the conspiracy theory pursued by Edgar Maddison Welch, a bogus and convoluted tale that casts Hillary Clinton and other top Democrats as the leaders of a child sex ring, are no more or less profane than so many others bouncing around the internet's seedier corners.

But the work of disentangling reality from a web of distortions dressed up as fact has become a persistent struggle for large segments of the population.

"People are constantly bombarded with information from so many different sources and it isn't always easy to work out what is true and what is false, and which sources are credible and which are not," Karen Douglas, a professor of social psychology at the University of Kent in the UK told CNN.

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Here's why the conspiracies are spreading:

What separates Welch and others spreading the theories online is not the craziness of their ideas, but how relatively common they are. Americans of all political stripes believe in conspiracy theories. And their most typical identifying trait, according to experts in psychology and media, is a desire to be deceived.

"Tens of millions of people believe in conspiracy theories," Dartmouth political science professor Brendan Nyhan told CNN. "There's a group of people that believe in a lot of them, but there's a much broader group that is willing to endorse them in certain cases. It's not a reflection of mental illness or pathology. It's a common thing that otherwise smart and well-informed people do."

What has changed, though, since the heyday of the John Birch Society in the 1960s, is the rate of proliferation and speed at which the dark whispers turn to public pronouncements.

"Someone like Alex Jones (of the Infowars website) can amplify the most effective conspiracy theories and spread them to a large audience," Nyhan said. "Sean Hannity, too. We've seen memes jump from the fever swamp online to Hannity and Alex Jones and even Donald Trump's Twitter feed very quickly -- people like that can harvest the conspiracy theories that they think are most interesting or entertaining or shocking."

Preying on weakness and creating the 'other'

The most prominent channels may change over the decades, but the insidious nature of the misinformation spreading these days is not fundamentally different from the lies peddled a half-century ago.

"You're giving power to people who are feeling powerless," said Bob Goldberg, a history professor at the University of Utah and director of its Tanner Humanities Center. "It's an antidote to powerlessness because giving the responsibility, pointing the finger, targeting someone gives people a sense that they know what's happening."

Conspiracy theories tend to spring from those two prominent desires -- creating a feeling of control where it doesn't exist and defining an enemy where it is absent or difficult to define.

In the former group, we find the 9/11 "truthers," who falsely maintain that the 2001 terrorist attacks on New York City and Washington were planned and executed by the US government, and the Sandy Hook "hoaxers," who believe that the December 2012 murders of 20 young students and six teachers never happened. Both forged their stories in the crucible of horrific, paradigm-shifting disasters.

Their distortions offered a reprieve to people overwhelmed by a perceived loss of control. And in targeting the victims, they have created -- at an unfathomable moral price -- a place to direct their rage.

Abbey Clements, who was working as a second grade teacher at Sandy Hook School in Newtown, Connecticut, when the shooting happened, has along with her colleagues and the victims' families been targeted by "hoaxers" with a range of goals -- some, she said, rooted in old political debates.

"Besides being bullying and hurtful, these conspiracy theories are just distractions and through all of this they are really trying to silence the victims and survivors of horrendous tragedies," Clements told CNN. "So people are not speaking out when they could be and trying to show what is really going on here, whether it's gun violence or something else."

In the case of "pizza gate," the invention offered a way for individuals with a searing dislike for Clinton and her allies to eschew any idea of reasonable disagreement -- and replace, as Goldberg said, "your enemy and create the 'other.'"

"The person that is against you is not simply wrong -- doesn't have a different opinion and they can be changed -- the person who is opposed to you is somebody who has committed treason, someone who has betrayed the country," he said. "That puts them in a different sphere -- that's somebody who needs to be punished."

Easy to believe, hard to explain

As they have played out on larger stages during the past two years, the anatomy of the conspiracy theory has become more familiar to even casual observers of media and politics. Like a virus, they come about simply and move rapidly, but can prove maddening or impossible to destroy.

"These stories are intricate and complicated -- far more so than reality or official explanations," University of Miami political science professor Joseph Uscinski told CNN. "People have a world view and when something happens, something is laid over that worldview. So when a Republican heard that (Supreme Court Justice) Antonin Scalia died, it isn't that difficult to feel that sense of loss knowing you're about to lose an institution to the other side and say, 'Obama must have killed him!'" -- even though that's false.

Just the facts?

The utility of fact-checkers in that environment can be difficult to predict. Ten years ago, Nyhan and a colleague presented a study on the effects corrected misinformation in news stories has on the people who consume them. Their findings were inconclusive and suggested that, in some cases, certain personalities would exhibit what they called a "backfire effect," and dig in deeper to their initial positions.

"Fact checking is vital but it's not always as effective as we like. It's the best response we have -- when appropriate," Nyhan told CNN. "But we should at least be circumspect about the idea that fact checking can counter the effects of misinformation especially with conspiracy theories because they're inherently unfalsifiable."

The logical tangle was on display just hours after the Sunday afternoon incident. Michael G. Flynn, the son of incoming national security adviser Lt. Gen. Mike Flynn, sought to defend the conspiracy theory with a perfectly impenetrable logical fallacy.