Independent MP Alex Greenwich says he struggled to advocate for his voters and the LGBTI+ community after Mark Latham's explicit, repulsive comments about homosexuals.
Mr 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.
Mr Latham's sexually explicit tweet was in response to an earlier post quoting the independent state MP describing him as a "disgusting human being".
Mr Greenwich claims Mr Latham's post defamed him by claiming he engaged in disgusting sexual acts and was not fit to be a politician.
He alleges statements by Mr Latham and published in the Daily Telegraph in April 2023 defamed him further by accusing him of grooming children in schools.
As the trial started on Wednesday, barrister Matt Collins KC said the tweet had dramatically affected Mr Greenwich.
"The impact has been so severe that he's found himself questioning whether he can continue to serve the people of NSW in public life," he told Justice David O'Callaghan.
From the witness box, Mr Greenwich denied suggestions by Latham's barrister Kieran Smark SC that he had been able to continue his advocacy without problems.
"I've always maintained the importance of having a stiff upper lip and putting up a brave face," he said.
"That lip though has been quivering."
Mr Greenwich told the court Mr Latham's defence angered and saddened him, while making his stomach churn.
In his public life, he said he had long tried to point out gay people were normal and like everyone else.
He denied Mr Latham's attempts to say he had gone into schools to talk with kids about sexual activity.
"I don't and I wouldn't," he said.
The online sparring match between the two politicians followed violent protests outside a church in Sydney's southwest where Mr 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, the court was told.
Dr Collins said Mr Latham's tweet had unleashed a torrent of abuse, including death threats, despite only being online for two hours and 20 minutes.
"Our case is that in (that time), the course of Mr Greenwich's life changed," he said.
The ex-One Nation leader had played on two-tired stereotypes - that gay people were somehow depraved and a danger to children - when making his comments, Dr Collins said.
The barrister said while his client had attempted to engage in a bona-fide debate arising out of the violent incident, his opponent took a different route.
"Mr Latham, rather than engaging in that debate, went as low as possible," he said.
The abuse, online and in messages to his Sydney electoral office, included claims Mr Greenwich was a groomer and a pedophile and that death was too good for him, the court was told.
The violent nature of the words led to panic attacks, anxiety and loss of confidence by the independent MP, Dr Collins said.
"He finds himself becoming overly emotional, crying, he is reluctant to attend large gatherings out of fear."
Mr Greenwich has also made a complaint to NSW Police about Mr Latham and filed a vilification lawsuit against him in the NSW Civil and Administrative Tribunal.
"I wanted the hate and abuse to stop," he told the court.
Under questioning by Mr Smark, Mr Greenwich denied his initial comment to a Sydney Morning Herald journalist calling Mr Latham a disgusting human being was intended to provoke.
"This was the first instance of political violence in an election period in Australia for some time," he said.
"There had been a campaign by Mr Latham to target vulnerable members of the LGBT community.
"Those two things combined, I believe my assessment was appropriate."
The hearing continues on Thursday.