Alexander Devriendt was at a standup show with his girlfriend a couple of years ago, when the comedian on stage unexpectedly turned on her, calling her a bitch and telling her to sweep up the stage, since that was all she was good for. She professed not to mind, but Devriendt was infuriated, not least because he couldn't retaliate. "Because it would seem like I wasn't getting the joke. I hated that feeling," he says, still bristling. "I felt so unmanly."

That experience fed directly into Audience, Devriendt's latest project with the Belgian theatre collective Ontroerend Goed. The show examines crowd behaviour in various cultural and political contexts, testing the extent to which people retain their individual identity and beliefs, and how easily their thought processes can be manipulated by those around them. One scene in particular stunned and appalled audiences at this year's Edinburgh festival, and will no doubt do the same in Plymouth and London this autumn. (Spoiler alert People planning to see the show, please look away now: it's when performer Matthieu Sys trains a video camera on a young woman in the audience and begins to insult her, telling the rest of the audience that he will stop when she spreads her legs.)

"Is it shocking? Yes," says Devriendt. "But I wanted a moment where the audience have to make a choice: even if they make a decision not to intervene, it's a decision."

The creation of the scene was itself contentious. Maria Dafneros, the only female performer in the piece, recalls: "We looked seriously at what we could do to divide the audience, what would be that one step too far. When we decided on 'spread your legs', I said, 'Absolutely not: it's sexual harassment. We cannot do that.'" But the fact that Dafneros was so repulsed by the idea was what persuaded her that it would work in the show.

Test audiences were involved throughout the rehearsal process. If those watching had been British, say the company, the scene may never have passed. "In Belgium, they're like, you're pulling this joke on us, so we'll play along," says performer Tiemen Van Haver. During the show, Dafneros's character condemns the scene, while Joeri Smet's counters that it's just a bit of fun.

"In Belgium, people are more on my side," says Smet. "In Britain, people are on Maria's side. The moral outrage is bigger – as is the need to express it publicly, and take a stand."

It's not the first time that Ontroerend Goed – whose name translates roughly as "feel estate" – have been taken aback by the controversy one of their shows has provoked in the UK. In Internal, which they brought to Edinburgh in 2009, audience members were taken one-to-one into private booths by the performers and seduced into revealing personal details about themselves – only to witness those details being broadcast for all to hear in the second part of the show. The company was accused of betraying the trust of its audience, something Devriendt regrets. "I should have seen that one coming. When you confide something to somebody, I think you [feel a] need to communicate. But it wasn't my intention to be mean about that."

He has, however, always sought to test the boundaries of what people will consider acceptable. As a teenager, he was expelled from school for publishing a magazine satirising his teachers. His favourite hangout at the time was an alternative jazz-poetry club in Ghent; it was here that he befriended Ontroerend Goed's other founder members, Smet, and producer David Bauwens, people he felt shared his aversion to rules. Initially, they were a poetry group, but one that sought to change the way poetry was performed. Their first proper show together, 2001's Porrer – "a mixture of porn, horror and poetry" – featured Smet as "a sort of Jesus-Hitler figure", and a scene in which Smet strangled Devriendt until he fell unconscious. Although Devriendt was in physical danger, the audience didn't realise. "Nobody believed [he was genuinely unconscious], because it was so absurd that we would do that," says Devriendt.

Although after that show they dropped the poetry and focused on the performance, it wasn't until 2005 that Devriendt began to think of Ontroerend Goed as a theatre company. The turning point came with the creation of a piece they called The Smile Off Your Face: "The basic idea for that was to change the whole experience of theatre. Normally you're with 100 people: [with us] you're alone. Normally you're immobile: let's make you mobile. Normally you can see: let's take that away." What resulted was a piece in which audience-members were blindfolded and bound into a wheelchair, then had each of their senses teased before a final, unsettling moment of intimacy with a performer.

The goal of that – and of every show Ontroerend Goed has made since – was to "show how your view of the world is mostly a projection of your inner world," says Devriendt. He admits he struggles to find the balance between confronting people and offending them. But he also thinks that audiences who feel manipulated might be shying away from a fact of modern life: that in a world of political spin and untrustworthy media, "we are being manipulated all the time."

• Audience is at the Drum, Plymouth (01752 230440) until 12 November, and Soho theatre, London W1 (020-7478 0100), from 6 December.