In fact the FBI has often hid the scope of Stingray operations from judges for precisely this reason.
Only one person was affected by it. The initial request was for anonymized data and the subsequent request for actual data was made for only one specific person.
It is already known that agent provocateurs are used to incite peaceful mobs. It would be no great difficulty to use a agent provocateur to give a probable cause to pull the lever that dumps the complete list of people in that mob with little effort.
Technology affords law enforcement great powers. But simply handing these powers over without judicial oversight and control can turn very dangerous.
You don't need to lecture me. I'm with you. In fact, I participated in the Restore the 4th protests just after the Snowden leaks.
What I'm saying is let's not cry wolf here. Yes surveillance technology can be used to set up a system of oppression. So can many other state apparatuses. If the state had such desire it could skip the middle man of surveillance and skip straight to martial law. That is why we have a system of courts and warrants and checks and balances etc.
A warrant for data highly limited in terms of scope in time and place isn't a threat to civil liberties. A blank check for a Nation State Actor to get any data it wants, anytime, without giving any cause is a threat to civil liberties. We make ourselves look bad when we confuse the two.
The problem is that those are worth nothing if judges and courts do not understand (or don't want to) the full consequences of carelessly signing those warrants.
In Germany we have some local courts which are "famous" for being very near to the police and will often rule against your personal freedom or accept half-cooked "evidence" from copyright holders (rather their shady lawyers) for purposes of spamigation and alike.
You can't trust in the court system to rule in favor of freedom here.
The crime itself is a violation of civil liberties.
I'm not in any way suspicious, just because I have been around the area where a crime has happened. As we know those blocks can be quite large so you will have lots of "suspects" whose only connection to the crime is being around a crime scene.
Then you question all of them and hope that something sticks with one of them. That is unprofessional and will lead to lots of problems once your neighbours get to know that you are suspicious of $crime because you were near $location.