Brandan Koschel attended the March for Australia protest alongside hundreds of others winding their way through Sydney's city centre.
The 34-year-old took the stage at the end of the march and endorsed neo-Nazi views before being immediately arrested by police.
He has pleaded guilty to intentionally inciting hatred on the grounds of race for his 40-second speech in which he twice called Jews the "greatest enemy".
Koschel wrapped up the speech by "heiling" white Australia and Thomas Sewell, the leader of Australia's most prominent neo-Nazi group, the now-disbanded National Socialist Network.
He also called for the release of jailed NSN lieutenant Joel Davis.
On Tuesday at Downing Centre Local Court, police prosecutor Adrian Walsh called the offending very serious, especially in the current social and political climate.
In an affidavit filed for Koschel's sentence hearing, his mother said her son had made a "mistake" and that he had a "heart of gold".
Those were things only a mother would say, Sergeant Walsh said.
"This was not a mistake," he told Deputy Chief Magistrate Sharon Freund.
Koschel watched the hearing via video link from Shortland prison in Cessnock.
He only spoke when Ms Freund asked if he could hear them.
Defence barrister Daniel Grippi said, by outlawing incitement of racial hatred, parliament had denounced serious conduct like his client's.
However, he said that hatred was subjective and "somewhat political".
"One's person hatred is another person's love," he said.
The hatred spouted by Koschel was quite typical, meaning it had to be denounced more heavily by the courts, he said.
But he described the offending as opportunistic.
"Perhaps not everybody should be given the opportunity to stand in front of a microphone," the barrister quipped.
Mr Grippi argued Koschel should be released from prison, having served 23 days behind bars, and handed a community sentence.
He would not reoffend, his lawyer said.
The arrest had had a negative impact on Koschel's family, who had been followed and sent letters.
"It's regrettable that in the current climate, our associations with people attach us to their views as well," Mr Grippi said.
Ms Freund will sentence Koschel on Wednesday.
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