Left-wing agitators GetUp loves boasting about disrupting its political opponents' events. Turn the tables, and it doesn't cope well at all.

Just days after MP Helen Haines was mowed down in a horrific attack that left her in hospital without both legs, GetUp held a launch event in Frankston for its so-called Fight the Right campaign, which has been relentlessly targeting the local One Nation candidate. The man accused of the attack had long supported the group and retweeted its posts many times. Knowing from experience how violent its supporters can get, I brought security along, just in case.

The first organiser I approached, Matt Maber, a former failed Greens candidate, insisted the attacker had "nothing to do with GetUp". Had he ever paid for a membership? "Not to my understanding." Had he volunteered? I was told I couldn't stay on site.

GetUp's tactics against the right, I was told, are the "same as any other political campaigning group". If that's true, why not run a candidate and let Victorians decide? The Prime Minister has urged everyone to tone down the rhetoric, but when I asked what that meant for GetUp, I got no answer.

Then the venue president came over and shouted at me to "get out" of his property while my crew and I stood in the public park. He said he would rent the venue to "anyone who wants to pay", even the Nazis. I doubt he would go through with it, despite his confidence.

The president then returned with what he called a "legal directive" to leave, insisting we were on private property. We weren't. The car park is Crown land, owned by the public through Frankston City Council, and I had advice that he had no authority to remove us from it during public hours. This is also a venue that took $1.75 million in government grants for its extension. I never set foot inside it, and I didn't leave.

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Most attendees wouldn't say where they were from. One woman, who teaches public policy at a university, said she wasn't a GetUp member and had come because she was worried about One Nation. She hadn't known the attacker was involved with GetUp, and when I invited her to speak with the One Nation candidate, who was there on the night, she declined. Another attendee wore a shirt celebrating GetUp's National Press Club stunt against Pauline Hanson.

Then the gate was shut with my team and me still inside. Holding someone against their will is unlawful, as far as I know, and every minute I was stuck behind that gate I was deprived of my liberty.

Organisers had warned earlier that "police are on the way". When officers arrived, I made it clear we were journalists working on a public interest story on public land, and that we had every right to be there. They backed down, and we carried on.

Once we were out, the One Nation candidate told me the campaign has turned on people who simply support him. The organiser of a local market had been so supportive that she waived his fee, then rang him almost in tears about three days before his first market appearance and asked him to pull out. People had been phoning her around the clock and threatening to boycott and protest the market. He pulled out. Last weekend a florist greeted him with open arms. Two days after his team posted photos of the visit, she phoned to ask them to take the post down because she had been threatened.

He's new to politics, but he won't be scared off.

"No, not at all."

Judging by the near-empty car park, GetUp's big launch scared off more of its own supporters than it did him.

GetUp and its mates want independent journalists shut out and shut down. If you want me on the ground asking the questions they won't answer, please chip in at ProtectAvi.com.