Thomas Sewell and three others pleaded guilty in the Victorian County Court to one count of violent disorder over the Camp Sovereignty incident in August 2025.
"I contest the facts," each man said on Wednesday after entering their plea.
The incident at the Indigenous protest site in King's Domain occurred after an anti-immigration protest in Melbourne's city centre.
The men, dressed in black, allegedly held down occupants of the Indigenous camp before kicking and punching them.
Five people were injured in the incident.
A number of witnesses will be called to give evidence in a pre-sentence hearing where contextual facts will be contested, Sewell's lawyer Dermot Dann KC said.
"Antifa and protesters causing violence to cars - that's the context," Mr Dann said.
The defence said witnesses will be called to provide their accounts about what other people were doing and their behaviours surrounding the incident.
Outside court, Sewell said he did not dispute "spontaneous violence on the day".
"What is in dispute is whether that spontaneous violence had causes and whether there was cause and effect of this," he told reporters.
Sewell said his group was provoked and suggested the average Australian would have responded the same way.
"What must be contested is that this was not an attack on Aboriginal people," he said.
Sewell and the other three men - Jake Crockett, Michael Saarinen and Nathan Bull - will return to court on November 9 for a directions hearing.
Bull has also pleaded guilty to a second charge of failing to provide his name or address to a police officer.
Five other men have admitted to their roles in the attack and will face a pre-sentence hearing in November.
Two others will contest their charges at trial.
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