You don't get MS-13 in the kind of operations that the populace have been protesting. If people are showing up with whistles and megaphones you have lost the element of surprise by such a long-shot what you are basically are getting are people who have to be there to wait for their kids to get back from school, or are sticking around because they need to go to their regular doctor appointment.

If they were getting gang members the protests would be useless because tactically they would be in and out every time before anyone could protest their operations.