From what I've seen, it's simply an aversion to mass scale surveillance, even in public setting. The worry being how easy it could slide into a tool used by the state for nefarious purposes (punish political dissidents, etc).
Where I am, the local speed cameras have annual documents about the street their on detailing pre-camera vehicle speeds and fatal (pedestrian) accidents and the decreases in both of them since the usage.
Afaik, the concern isn't that it "could slide" its that flock _is used_ by say Texas to monitor out of state abortions. That isn't solving street crime and certainly didn't benefit the local residents.