It's a very dangerous strategy, but you're kinda right. My understanding is that armed protests tend to ironically be the most peaceful because cops tend to be too scared to challenge you. However, that only works if the cops think they're outnumbered, so you have to have a lot of people openly carrying and hope the cops don't decide to escalate past basic riot gear.
Edit: you also have to be prepared to pull the trigger. Like, seriously. If you're open-carrying during a protest, you'd better be prepared to kill a cop or two in the event they decide to challenge you. If you don't, then they'll know the guns are just for show and will be quicker to challenge you in the future.
You need to absolutely out number the police and have enough trigger discipline NOT to fire first. Otherwise the armed protesters would just be put down and the cops would control the narrative. Look at the 60's era Black Panther armed protests. They had enough guns that the cops weren't interested in escalating.