Walking in public using a phone or camera to record is not unlawful assembly. Yelling is not unlawful either, nor is blowing a whistle or using bad words.
The Civil Rights movement comes to mind right now. Successful assembly of people demanding change, to stop what was wrong. Of course, there were plenty of people who didn't support the protesters, to put it mildly.
Women once marched to get the vote. They were mocked, abused, jailed in the proces - probably told they brought danger on to themselves by critics - but they did it. (Thanks, ladies.)
I'd mention the American Revolution, but someone will think that's too far off-topic, I suppose. And, those Patriot protests were not peaceful like the those we see in Minneapolis. One of the big grievances of the Revolution was search and seizure without warrant, and that lead to our 4th amendment. There was no warrant today and the donut shop refused to admit the agents. The local authorities got a warrant to access the crime scene, and the Feds didn't honor it.
It's legal to be in public.
jmo