The story in that comment does sound consistent with behaviour at similar rallies, though. When there was that protest outside the Melbourne military expo last year, random people just walking past were being assaulted because they looked like attendees (committed the crime of wearing a suit). It's also worth noting that nothing in that linked Facebook statement actually disproves the anecdote you shared:

So what we have here is a noisy but strictly non-violent footpath protest, that didn’t block roads, driveways or building entrances, during which even the Queensland Police (who love creating bullshit excuses for arresting activists) couldn’t find ANY examples of assault, hate speech, trespass or anything else for which they might justify arresting someone.

Here's a news article that does a better job of representing the event than Courier Fail.

If you can find a way to access it, here's the video. It's honestly a shame to me that Sriranganathan continues to almost exclusively use Meta social media properties. As a politician I get that he needs to be where the people are, but as an anarchist you'd think he'd at least try to be promoting federated social media. But unfortunately as it stands, to be involved in political activism in Australia requires being on Facebook.