But Dunedin city councillor Andrew Whiley, who was present at the conference, said it was the protesters who were out of line and not the authorities.
Climate Liberation Aotearoa spokesman James Cockle said some of the protesters snuck into the Edgar Centre yesterday morning to disrupt a cruise and tourism meeting held by Enterprise Dunedin.
Others picketed outside to protest the impact the cruise industry has on climate change.
The protesters were there for about 20 minutes before security intervened, and Mr Cockle said they were initially heavyhanded.
"The security was initially a bit rough. They assaulted some of our members, grabbing them, pulling them off their feet to remove them, but after a moment we were all calm and the situation was de-escalated," he said.
"I think that’s a heavy-handed response. That’s over the top," he said.
Senior Sergeant Anthony Bond disagreed, and said all the protesters, including those who did not enter the conference room, were complicit in disrupting a private business.
"They’re still a part of the group, they’ve been aware of the other group’s activities, and they were still on private property, which is the carpark area, which is part of the Edgar Centre.
"So we made the decision to trespass everyone involved," he said.
Cr Whiley said that it was the protesters who were the aggressors.
"The activists were picking up chairs, grabbing them, they didn’t care where they went. One person that I know was hit in the leg,
"They started getting in the faces of everyone, saying ‘come on, come on’, that sort of thing," he said.
Mr Cockle said there were about 60 cruise ship, local government and tourism officials discussing the upcoming summer season.
The protesters were there in the hopes of cancelling the meeting.
"We entered the conference room just before the event had started, but while the participants were there.
"We addressed the audience there with megaphones and let them know we were shutting down the conference.
"Others were stacking up chairs and putting them aside to signal that we were closing it down, and we politely instructed the participants to leave," Mr Cockle said.
The protesters were taking action to save lives because cruise ships coming to Dunedin produced enough carbon dioxide emissions to cause about 800 deaths due to climate-related causes.
The protest yesterday was just the start of their fight against the cruise industry and the damage it caused, Mr Cockle said.