It ranks among the lowest of acts: to give terminal cancer patients hope that they can survive their disease with your inspiring – but, it turns out, untrue – story of how you beat the odds simply by eating healthy foods. Unforgivable behaviour, no question.

But it's also unforgivable to dupe the media. To build a lucrative health empire on the back of a lie spread though the papers and on morning television, exposing those who were sucked in by your deceit (and making a tidy fortune in the process) tends not to go down well in newsrooms.

After watching 60 Minutes on Sunday it was difficult to know which of these crimes Belle Gibson was being punished for.

For nearly three-quarters of an hour 60 Minutes chief inquisitor Tara Brown grilled Ms Gibson about her story that she beat cancer and a brain tumour using alternative therapies. She had initially told her "amazing" story on Instagram in 2013, gaining a substantial following (the account still has 174k followers even though all the posts have been deleted), then launched an award-winning health app in the Apple Store on the back of a book deal struck with Penguin. That her story turned out to be pastiche of overstatements and untruths upset quite a few people.

The 60 Minutes interview was meant to clear the air. It was the chance for Ms Gibson to explain, to apologise, to make sense of behaviour that was so cruel to people so undeserving.

The erstwhile darling of the miraculous remissions club didn't fare well under the spotlight. She stammered, paused too long, looked nervous and uncertain as Brown probed and prodded and demanded answers, exposing inconsistencies in Ms Gibson's stories, frequently imploring her hapless subject to just tell the truth.

"Do you know what the definition of truth is?"

"What is a lie?"

"Why can't you just tell the truth?

"Oh, Belle, Belle, Belle, Belle..."

It was relentless stuff but Ms Gibson stuck to her line: I didn't have cancer or a brain tumour, so my story of miraculous survival was not true. But I thought I did; I wasn't deliberately deceiving anyone.

It was a subtle evasion that Brown would not accept. Again and again she hammered the witness as she tried to demolish her account and get her to confess.

She even tried a cross-examination ploy known to every TV lawyer worth half their fee. After a relentless grilling, scoffing at the answers as though she felt insulted by the lies being told to her and aggressively pushing and pushing and pushing yet more, Brown offered Ms Gibson an out.

In a gentler, more sympathetic tone, Brown asked: "I just wonder, Belle, if – and I don't know if you're at a stage where you'll ever admit it – but whether you just didn't know what you were getting yourself into. You probably thought you weren't doing any harm … you thought you could get away with it."

It was the moment the witness in the box is meant to grab the chance to finally end the charade, to come clean, to fall to their knees relieved of the burden of so many lies told and have the nice interrogator put a comforting arm around them and say, "There there, everything will be OK now you've told the truth. It's over now."

But Ms Gibson was having none of it.

"There was nothing to get away with, Tara."

"Of course there was," the prosecutor shot back, treacle still dripping from her voice. "There's adulation, there's sympathy, there's a community who loves you. There's huge amounts to get away with."

Nup. Ms Gibson didn't give an inch.

It was tense stuff. Ms Gibson did her best but against the might of the medium of television – including an editing suite that can freeze your face on a guilty expression and add a bucketload of sinister, dramatic music just before an ad break – she never stood a chance.

To shift from courtroom metaphors to the boxing ring: the exchange between the combatants was a constant barrage of short-arm jabs either clumsily parried by Ms Gibson or taken square on the chin. By the end she was bruised and battered, her credibility shredded. She remained standing but was clearly the loser – although were you to ask her she might insist she won on points. There did seem to be a fair amount of self deception on display.

In a high profile interview like this there are two kinds of transactions going on: a commercial transaction and a truth transaction.

In the first transaction, the parties are focused on numbers. For the journalist and TV network it's about ratings and advertising dollars. For the interviewee, whose earning power has slipped from stratospheric as a self-promoting miracle cancer healer to zero as a self-confessed fraudster, it's the (reported) $45,000 interview fee they're being paid to take their medicine in the public square.

In a truth transaction, both parties have the same goal: the journalist wants to uncover and report the truth, the whole truth etc and the penitent wrong-doer wants to tell a version of the truth to achieve some reputation repair.

In the commercial transaction truth is not enough, there must be friction and a narrative of good vs bad in which the baddie gets their dues. That's what makes the punters come back after the ad break.

The truth transaction is a test of quality journalism in which uncovering what really happened is its own reward. It's what real journalists live for.

In an age when it is so easy to deceive online, to create personas and stories that can be so difficult to expose as false, the search for truth is the journalist's most important function.

Did we get the truth on Sunday? Maybe. Some of it, at least. But it wasn't the whole truth.

The more depressing question for the journalist to ask is: do people even care about the truth?

Don't know. Hope so. What we do know is that they like a public lashing.

And that's what 60 Minutes gave us.

Gordon Farrer is an Associate Lecturer in Journalism at RMIT University. His Twitter handle is @infactability.