I think it would really help both in terms of outcomes as well as the perception of police if they gave this kind of clear description of what's going to happen. As it stands now, the curfews aren't enforced with any kind of regularity, so they just cause confusion.
- curfew: a curfew is an extreme tactic that deprives many people of their civil liberties without due process. There are legitimate reasons for curfews to exist at times, but dispersing peaceful protest is not one of them.
- use of tear gas: this is (quite literally) prohibited under the Geneva protocol even in times of war.
- "difficult for police to determine": this suggests that because the job is difficult, the police have leeway to indiscriminately punish whomever is nearby.
Again - I understand why you'd make the argument you made, but the fatal flaw is that it is founded on an utterly dystopian premise. The response from police across the country is unjustified, and a rank violation of everything that Americans supposedly hold dear.