it is difficult to wrench someone when you do not know who they are
Someone knows who they are and they can bash different skulls until one of them gives them what they're looking for.
I mean they have a lot of tools to figure out who you are if they catch you at a rally or something like that. Cameras and facial identification, cell phone location tracking and more. What they also want is the list of people you're coordinating with that aren't there.
This is accurate, but the important point is that threatening people with wrenches isn’t scalable in the way mass surveillance is.
The problem with mass surveillance is the “mass” part: warrantless fishing expeditions.