That's an oversimplification, it's when cops start keeping track on people based on such data, plus analyzing their behavior as a group.

Is it though? People are willfully submitting all this information to American companies that we know share info with police.

When cops start using geolocation data that isn't enabled I'll be more worried.

Peaceful protest sometimes attract a few bad apples. Things have ways of going wrong. If the police weren't on top of these activities, they would look massively incompetent in their job.