On Thursday night, at a town hall in New Hampshire, Donald Trump nodded along and even seemed agree when a supporter declared, "We have a problem in this country, it's called Muslims," then went on to ask, "When can we get rid of 'em?" The man also declared President Obama to be Muslim.

The supporter also said something else: "We have training camps growing where they want to kill us."

The question about the training camps wasn't incidental. In fact, even the Trump campaign is insisting that's what the question was about — and that that's what Trump was responding to when he said, "We're going to be looking at that and plenty of other things."

The Trump supporter was talking about a conspiracy theory that been festering on the far-right fringes of American political discourse: that Muslim American communities are sheltering secret terrorist training camps in the US.

The very basics of the "Muslim training camps" conspiracy theory

"Fears of 'Muslim training camps' have simmered on the far right for years, especially since the rise of the Islamic State," Jenna Johnson writes in the Washington Post, adding that right-wing media sometimes claim there are dozens of such camps.

These stories make it into more mainstream right-wing media as well. Johnson links to a January Fox News clip in which Bill O'Reilly hosted a member of a far-right group who claimed that Muslim Americans are organizing secret paramilitary communes poised to commit acts of terrorism. O'Reilly and the guest discussed the supposed Muslim training camps at length. On Fox Business, also in January, Lou Dobbs hosted the same group to repeat these claims.

This conspiracy theory has prompted attempts at far-right violence in the past. Just this spring, FBI arrested a Tennessee man named Robert Doggart who was plotting to lead a far-right militia on a killing spree against a heavily Muslim community in New York state.

Doggart believed the community was a "Muslim Jihadist Training Camp," according to a post he made on his web site. He wrote, "Given the recent beheading of an American Journalist by the treacherous ISIS group, the Islamic networking that is underway in America, and the threats directed at us, there is no choice but to engage this topic, face-to-face, on location."

Why this conspiracy theory is growing, along with incitements to anti-Muslim violence

The implication and basis of the conspiracy theory are pretty clear: that the 2.6 million Muslim Americans in this country are not equal citizens who happen to follow a different faith, but rather a frightening enemy within that must be confronted, violently if necessary. Calls for a mass ethnic cleansing campaign against Muslims, like the one the Trump supporter implied is necessary, are merely the next step in that horrifying logic.

Like much of the rising tide of Islamophobia in America, this conspiracy theory has been around for a while but has grown since the emergence of ISIS, helped along by US media coverage that frequently conflates ISIS with all Muslims and suggests, as CNN often does, that Muslims are inherently violently people.

The conspiracy theory also feeds into far-right fears about demographic change, and a belief that, as white Christian Americans lose their demographic dominance, they will come under physical threat as well.

These fringe extremists see the world as divided into racial and religious groups, and believe that they are already under imminent physical danger from people who look different from them. Within that warped worldview, pre-emptive violence against their perceived enemies would be entirely justified.

More media-savvy groups, such as the one Fox News has hosted, will simply point out that it's a shame that restrictive laws make it impossible for the FBI to arrest the people in these training camps. But this is just a way of subtly suggesting that America would be safer if we could take away the pesky civil liberties of the members of these "Muslin training camps," who, recall, are in fact innocent Muslim American families.

That is what led Robert Doggart to plan to attack innocent families in New York, and it is what led Trump's supporter to call to "get rid of" Muslims. So while Trump's campaign is trying to spin this as Trump only agreeing with the call to "look into" Muslim training camps, make no mistake that when far-right groups talk about "getting rid" of Muslims or even just Muslim training camps, what they are actually talking about is large-scale discrimination and perhaps even violence against Muslim American families.

This is not a problem of just the far right

The New York town that Doggart was planning to attack, by the way, had been featured prominently in the January O'Reilly segment as a secret training camp.

This is to say that, while Trump and his supporter are being covered as just a wacky clown candidate refusing to confront a wingnut supporter, in fact this episode is a direct outgrowth of anti-Muslim incitement and bigotry that has been promoted for months on right-wing outlets such as Fox News.

It is not a problem of Trump and the far right, but rather a problem of the mainstream right, and indeed it is the inevitable extension of Islamophobia that appears regularly even on non-partisan outlets such as CNN. That's not to say that these more mainstream outlets deliberately encourage ideas like the "training camps" or violence that they can lead to, but the way that their coverage openly entertains subtler Islamophobic tropes, such as the idea that Muslims are inherently violent, feeds into them nonetheless, and is part of the problem.