The libs going to these protests aren't joining the left anytime soon.
They're most likely a scratch away from going full fascist vs. comrades in waiting. Think about it: these protests are on a weekend midday attended by a whole lot of well-off-enough white people with their "brunch" signs and costumes. This is a performance that they can say they did to their coworkers in their comfy office jobs on Monday.
You know who wasn't there? All the service workers who had to work during the weekend. All the people working 2+ jobs to survive. People without childcare. Neurodiverse people who get overloaded by the sensory input. People experiencing homelessness. Those people are potential comrades because they are the ones most exploited by Capital right now. The people serving brunch to these libs are the people to talk to, start slipping flyers, having those 1:1 organizing conversations with.