"They" are public bodies operating ALPR devices; in the main, municipal police forces, though obviously other public bodies (like the Illinois State Police) operate them as well.
The antecedent of the first "that" was "the use of cameras to detect cars with politically disfavored bumper stickers".
I am, yes, dismissing the concern that ALPRs are being used to detect cars with politically unfavorable bumper stickers. I think that if advocates for ending our Flock contract had come to the board table with that concern, rather than the quality of Illinois LEADS, we'd still have the cameras up.
The antecedent of the second "that" is "organizing around easily dismissible movie-plot concerns, like that municipal police are going to dragnet for people with anti-police bumper stickers". Unwinding the sentence, the "big deal" is, as I just said, that centering implausible risks takes real risks out of focus, and gives ammunition for advocates of the cameras --- of which there are a great many --- to push back on efforts to get the cameras down.
I spelled the "deeply problematic" things out elsewhere on the thread.
Feel free to tell me more about what Bloomingdale was doing with their cameras. With no detail, I'm inclined to believe the force simply didn't give a shit about the description field in the search request, because no serious, rigorous effort was made to regulate ALPRs in Bloomingdale, and so there isn't much signal in the logs.