The man suing Colin Craig didn't defame him, he exposed him, and the former Conservative Party leader "must be stopped", a jury has been told.
Taxpayers' Union executive director Jordan Williams is suing Mr Craig for nearly $1.4 million over comments made in a pamphlet sent to 1.6 million homes and a press conference in 2015.
He says Mr Craig accused him of spreading lies about the reasons behind the sudden resignation of Mr Craig's press secretary, Rachel MacGregor, two days before the 2014 national election, which led to Mr Craig stepping down the following year.
Mr Williams says he went to senior party officials after Ms MacGregor confided in him about alleged sexual harassment by Mr Craig, including touching, comments, and romantic letters and poems.
Closing the case for Mr Williams in the High Court at Auckland on Wednesday, lawyer Peter McKnight said when Mr Craig publicly announced he would "sue the schemers" - and Mr Williams for $300,000 - he had attacked Mr Williams' honesty and integrity.
"Why did Mr Craig not sue Mr Williams as he so publicly threatened?"
Mr Williams had just turned the tables on Mr Craig with the current lawsuit in order to defend his reputation against "extremely damaging remarks", he said.
"Finally [Mr Craig] found someone who would stand up to him," he said, listing lawsuits Mr Craig had taken against satirical website The Civilian, journalist Steve Braunias and former Green Party co-leader Russel Norman.
"There really must be a stop to this person. He must be stopped from ruining so many lives."
Mr Craig's lawyer, Stephen Mills told the court Mr Williams had broken Ms MacGregor's confidence in going to party members, leaving her "horrified".
But Mr McKnight said Mr Williams was tormented about whether he was obliged to breach her confidence to warn others that had attached their reputations to Mr Craig.
"In the end, rightly or wrongly, he decided to act."
He said Mr William's allegations had only been the cherry on the cake, after years of rumours about his relationship with Ms MacGregor.
"If anyone is to blame for Colin Craig's political demise, it is Mr Craig," he said.
"I suggest Mr Williams did not defame Colin Craig, he, in fact, exposed him."
Earlier Mr Mills told the court while Ms MacGregor's role could not be excluded, the case was really about what Mr Williams told party officials and whether Mr Craig was just defending himself while his reputation was being "shredded".
Mr Mills said a number of things said about Mr Craig were not true.
Mr Williams had incorrectly told party members there had been a sexual assault, that Mr Craig had sent a sext and Mr Craig's relationship with Ms MacGregor was one way, he said.
But Mr McKnight said Mr Williams had never lied.
"He relied on Colin Craig's own words. These were the words of a fundamentally flawed man."
The trial is in its fourth week.