The lies multiplied so rapidly Cori Langdon could hardly keep up. The taxi driver’s cellphone video of the Las Vegas mass shooting was being widely republished by conspiracy theorists, who were using it as “proof” that the massacre was staged by the government and that Langdon was an “actor”.

Langdon thought that if YouTube and Facebook removed some of the content, the online attacks and bogus stories might stop spreading. But it wasn’t so simple.

When some footage was taken down, conspiracy theorists saw it as further evidence that Langdon was involved in a cover-up. Some told her they were worried the FBI had gotten to her.

“It just fuels them even more,” said Langdon, who was harassed online even while being hailed by some as a hero for picking up passengers at the Mandalay Bay shooting that killed 58 people in October. “These conspiracy theorists love their guns. They are freaked out and paranoid.”

Concerns about conspiracy theorists bullying victims of mass shootings have escalated this month as student survivors of a Florida high school massacre have become vocal proponents for gun reforms, making them prime targets for online abuse. Google and Facebook have faced particularly intense scrutiny for their role in spreading false stories claiming teenage survivors are so-called crisis actors hired to promote gun control.

Cori Langdon, a Las Vegas taxi driver who helped save people during the massacre, faced online abuse from conspiracy theorists. Photograph: Jacob Kepler/The Guardian

But recent efforts to restrict offensive posts have shone a harsh light on a seemingly intractable problem of the modern conspiracy theory epidemic: that censoring the content can reinforce and enhance false beliefs and that there is no easy way to change the mind of a conspiracy theorist. Some wind up on alternative platforms.

Social media companies taking down content and mainstream news coverage of hoax claims can also drive traffic to those sites creating the questionable content. That appeared to be the case this week with Infowars, a rightwing website that has fueled “crisis actor” claims and is facing consequences from YouTube as a result. Radio host Alex Jones, a leading conspiracy theorist and far-right pundit, has used YouTube’s clampdown to drum up interest in his attacks on the Florida students, presenting it as a “free speech” issue.

“If you believe your institutions are conspiring and then you expose it and then they ban your speech, how could you not think that that’s part of it?” said Joseph Uscinski, a University of Miami professor and conspiracy theory expert. If Jones and Infowars continue to face YouTube censorship, he added, “it will convince his fans that he’s on to something.”

Those people are really stuck. They truly believe it, and it doesn’t matter what you say

There’s no easy solution, though many agree that YouTube and Facebook could do a better job removing content that constitutes harassment and preventing its algorithms from actively promoting fake news.

Infowars is reportedly one strike away from a YouTube ban, though Jones has a long history of offensive material, most notoriously spreading claims that the 2012 Sandy Hook massacre that killed 20 children was a hoax – a theory that led grieving parents to face death threats. If permanently banned, it’s unclear if Jones would end up hosting his own videos or using a platform like PewTube, which was created for “alt-right” users kicked off mainstream sites.

In some cases, fringe commentators with massive online followings have tried to push boundaries by avoiding explicit hoax claims and instead cast doubt on shooting survivors by simply “raising questions”.

Americans strongly opposed to gun control are susceptible to believing this kind of content, especially if the creators are facing threats from the “establishment” media or Silicon Valley.

Emma Gonzalez, a Stoneman Douglas senior, walks with fellow students. Conspiracy theorists have claimed outspoken survivors are ‘crisis actors’. Photograph: Joe Raedle/Getty Images

“You’re motivated to attack information that is not consistent with your beliefs. This is just a human trait,” said Colleen Seifert, a University of Michigan psychology professor, adding that when pro-gun conspiracy videos are suddenly removed, viewers can become further entrenched in their beliefs. “Absence of information might feed conspiracy arguments, because there’s no explanation for the disappearance.”

Uscinski argued that efforts to expose harmful conspiracies can backfire, noting that a leading Sandy Hook conspiracy theorist became well-known after a local newspaper wrote about his blog. “Maybe it should be ignored.”

Brock Matejka, whose brother survived the Vegas massacre and was labeled an “actor” online, said he tried to argue with conspiracy theorists attacking his family, but got nowhere: “Those people are so set in their ways. They are so far gone.”

When his brother Braden took down his Facebook page due to the threats and harassment, conspiracy theorists were emboldened, said Brock: “That was their proof that he was faking.”

Langdon said she was happy to see some videos attacking her disappear: “They just make me sick.” But months later, she still fights with strangers on her Facebook page, trying unsuccessfully to refute the conspiracy beliefs.

Mike Cronk, a retired teacher and Vegas survivor also attacked by conspiracy theorists, said it was painful to watch the Florida teenagers face harassment and that the tech companies “should be held accountable”.

The platforms should not let the abuse spread, especially considering how impossible it is to change the perspectives of believers, he added: “Those people are really stuck. They truly truly believe it, and it doesn’t matter what you say.”