They should all hammer on the van with their fists, or slap it, better still. The noise will be deafening.
That probably would have resulted in violence. What this crowd did was just at the right level: making people feel shunned, rather than threatened. They're all masked up—they can nope out of this at any time. It might feel like they're getting away with it, but if they go back into their holes and don't come out again, that's a good outcome. If working for ICE becomes a job nobody wants, that's a good outcome.
The last thing we want is them digging their heels in.
They should feel shunned. Nobody should be working for ICE. We want them to quit in droves instead of being Nazi filth.
"Filth" is a word Nazis use to refer to untermenschen. I would suggest that this is not helpful to use against them—it actually reinforces their worldview: that some people are real people, and other people are "filth."
What I really want is for these folks to find their way back to civilization, not for "us" to declare victory over them by making them into a permanent underclass. See e.g. Rwanda justice and reconciliation process.