It’s the kind of scandal that has become ubiquitous in the past few years: someone uncovers an offensive social media post or problematic previous bit of work from a public figure’s past. It normally ends with a public apology, and often a firing.

There have been at least three such stories in the past week. On Sunday, James Gunn, the director of Guardians of the Galaxy, was fired by Disney after 10-year-old tweets surfaced in which he made jokes about rape and pedophilia. Days later Dan Harmon, the creator of Ricky and Morty and host of the Harmontown podcast, apologised after an old sketch, in which he appears to rape a baby doll, resurfaced. Around the same time, an old standup bit by Trevor Noah also found its way online, in which he was making offensive jokes about aboriginal women in Australia.

What links Gunn, Noah and Harmon is the persistent criticism of Donald Trump. Harmon has previously suggested that the president would prefer the votes of Nazis to non-Nazis. Gunn previously offered to donate $100,000 to a charity of Trump’s choosing if he stepped on a scale in public to prove the weight on his medical report wasn’t fraudulent, joking he was part of the “girther” movement. Noah is the host of the Daily Show, which takes Trump to task on a nightly basis.

While few have disagreed that the jokes the three men made were repulsive, the way they found their way back onto the internet was part of semi-coordinated attempts by the “alt-right” to weaponise offensive material as a way of getting liberals fired.

The Harmon video, a parody of the TV show Dexter, first screened as part of the comedy festival Channel 101. In it, Harmon is shown breaking into a house and abusing a baby doll. It resurfaced on a thread on 4chan, the online message board beloved by anime fans, internet trolls and the alt-right, then moved to the Reddit page r/The_Donald, a major message board for Trump supporters and the alt-right. On 4chan, in between swastikas, antisemitic images and countless uses of racial and homophobic epithets, users argue that Harmon should be taken down as retaliation for what happened to Roseanne Barr.

Barr was fired from her eponymous ABC show after a posting a racist tweet in which she compared Barack Obama’s former adviser Valerie Jarrett to an ape. “Think of Roseanne Barr and all the other much less rich, much less famous people who have had their lives destroyed,” writes one anonymous user. “We must use these tactics against them as effectively as they’ve used them against us. It is the only way to win.”

On Reddit, there are numerous threads about Harmon from the past 48 hours, with comments such as: “They went after us for making jokes a lot less worse than this, we warned them it would backfire on them too, but they don’t listen do they?”

Harmon has said in a statement: “Nobody should ever have to see what you saw and for that, I sincerely apologize.”

‘Twitter is just modern-day gladiatorial combat’

The tweets that led to Gunn being fired, which also included jokes about peadophilia and rape, were surfaced by Mike Cernovich, an alt-right blogger and conspiracy theorist best known for spreading the Pizzagate conspiracy theory.

He boasted of his role in Gunn’s firing to online publication The Wrap. “I enjoy just the raw human visceral reaction of jumping into the arena and just swinging the hammer and seeing what is left over afterwards. Twitter is just modern-day gladiatorial combat.”

Cernovich said at the end of 2017 that he had seen the success people had in getting conservatives fired for offensive tweets and realised the right could employ the same tactics. “We found over 100 far leftwing journalists with fireable tweets. 2018 this project goes live,” he tweeted in December.

Cernovich has largely made good on his threat. He spread a Roman Polanski joke tweeted by MSNBC’s Sam Seder almost a decade ago. Seder was fired, though later reinstated by the channel.

Cernovich has also targeted comedians Patton Oswalt and Michael Ian Black. He surfaced one of Black’s tweets, which read: “I don’t like watching ‘iCarly’ with my daughter because there is nobody on that show I want to molest.”

Also on Twitter, Trevor Noah’s old stand-up routine was shared by the Australian Rugby player Joe Williams who doesn’t appear to have any political motiviation.

Alt-right channels on Reddit, such as r/thedonald, have been revelling in the controversy. The top comment on one post about Noah reads: “Liberal sensitivity is dialed up so fucking high that it was only a matter of time before they all started attacking each other.”

• This article was amended on 26 July 2018 because an earlier version referred to the subreddit r/thedonald, when a r/The_Donald was meant.