

You have a very poor understanding of how these critical masses work, they do NOT function like normal protests, at least in the US.
Most critical masses of cyclists are intentionally made to be spontaneous, barely organized, and they do not give prior warning to locals (through the local media or such), the government, or even the police. The whole point of the intentional disorganization to escape the authorities when they eventually come in to restore order. The reason why they’re called “critical masses” to begin with is because large turnouts is the only requirements of these events. There is no organization or leaders or hierarchy or anything to hold accountable.
So what happens is unsuspecting locals going on about their day get met with a mob of cyclists who are blocking traffic, ignoring any and all established safety laws, and disrupting the flow of the city. The people who do come across them don’t know where they came from, where they’re headed, or what they’re going to do next.
That’s why you can’t “go around them” like you’re suggesting. You’re basically trapped in your car until they go away. These events put the cyclists in danger and they put the drivers in danger. That’s why they’re considered dangerous. If they functioned like how you imagined they functioned, then way less people would have an issue with them.
A big part of the problem is that they DON’T do this. If they did then people can plan ahead of time to avoid running into them, and way less people would be annoyed with them. But that’s not how they operate, these events aren’t protests because they’re so disorganized. There’s no leadership, no organization, nothing. They also don’t give any notification to locals, law enforcement, the media, or their local governments. This why they’re considered dangerous, it’s because this disorganization puts the cyclists and drivers in harm’s way.
Most people who run into them, like the woman in the video, do so without prior warning. They’re just going about their day when they’re met with a mob of cyclists who are ignoring the established safety laws and blocking traffic. You have no idea where they came from or where they’re going. Their unpredictable. Yes, this woman filming and driving is being reckless, but she’s not the only one in the video who is.