The only safe way to analyse the risk is to assume the worst case scenario. The Ferguson police are the worst case scenario: to quell a protest they deploy violence, then complain when the protest becomes violent.

As a result of this, the police will feel justified claiming "imminent risk of death or great bodily harm" any time two or more #insert <target_demographic.h> are together in one place.

Then you just do this often enough that the judges don't have time to review every case.

Don't dismiss as ridiculous what is simply an extrapolation from current practise.