An explicit tweet sent by Mark Latham caused homophobes to flood a Sydney MP with offensive messages but also lowered his standing with those sympathetic to him, a court has been told.

Alex Greenwich has sued the former NSW One Nation leader for defamation in the Federal Court over a tweet sent in March 2023, days after the state election.

Latham’s explicit tweet describing a sex act was in response to a post quoting the state MP describing him as a “disgusting human being”.

Greenwich, who is gay, claims the former federal Labor opposition leader’s post defamed him by saying he engaged in disgusting sexual acts and was not fit to be a politician.

He is seeking damages as well as aggravated damages, including because Latham refused to resolve the case by apologising.

On Friday, the independent MP’s barrister Matt Collins KC said his client’s reputation had been damaged because the tweet triggered a flood of homophobic messages online and to his Sydney electorate office.

Justice David O’Callaghan was taken through a number of graphic and offensive messages received by Greenwich.

One letter included a swastika and a derogatory term for homosexual men.

Several messages suggested the Sydney MP should be killed or would be better off dead, including one referring to a dark chapter in Sydney’s history involving a spate of assaults and murders against gay men in the 1990s.

“I am not homophobic, one of my family is gay, but he doesn’t carry on like the likes of you,” one man wrote in an email.

“You are a disgusting human being and your actions are even more disgusting, how dare you represent Sydney,” another man said in a voicemail left at Mr Greenwich’s office.

Collins said his client had never seen anything like the abuse that he received after the Latham tweet.

“It’s the viciousness or the reference to things like dung and poo and faeces and s— that illustrates that Mr Latham’s comments hit their mark,” he told the court.

“No one was motivated to express themselves in anything like this form until Latham whipped up this frenzy.”

The tweet turned Greenwich from a proud member of parliament into a representation of an unhygienic sex act, the judge heard.

“This tweet reduced him to a filthy sex act, it caricatured him, it exposed him to ridicule,” Collins said.

“It led in the real world to people saying that they think about him every time they go to the toilet.”

Even those who were sympathetic to Greenwich, such as Greens Senator Sarah Hanson-Young, changed their view and started pitying him because of the tweet and abuse, the court was told.

Comments from Latham published in an April 2023 article in the Daily Telegraph were also defamatory in suggesting that he went to schools to groom children to be gay, the court was told.

While the One Nation leader did not explicitly say this, his remarks were “pregnant with insinuation and inviting readers to indulge in loose thinking”, Collins said.

The barrister attacked Mr Latham’s claims that the tweet was his honest opinion, arguing the politician did not have any facts about what Greenwich did privately in his bedroom or said when he spoke to children at schools.

A defence that he was protected from defamation because he was responding to provocation should also fail, he argued.

Latham did not make a proportional counter-attack towards Greenwich, Collins said.

“He moved into an entirely extraneous, divorced-from-reason, vilifying attack in the nature of retaliation.”

The online sparring match between the two politicians followed violent protests outside a church in Sydney’s southwest where Latham was giving a pre-election speech in March 2023.

About 250 mostly male counter-protesters violently attacked police and 15 LGBTQI protesters who had set themselves up outside the Belfield church.

Justice O’Callaghan has reserved his decision.

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– AAP