You have to know what you’re dealing with in this situation. These are peaceful people who mean no harm to anyone. They may get agitated or seem combative, but they’re merely trying to stand up for their rights or the rights of others. Finding your authority challenged in such a way is something you probably don’t deal with as often as you probably should. As more and more people learn what their rights are and how to assert them you are going to encounter these situations more and more.
So what do you do? You could find some excuse to arrest this person, maybe even attempt to entrap them into not obeying you or something else that’s not really a crime but just a misinterpretation of the law. You might get them off the street for a day or 2, but these charges will likely not stand up in court and will cost the taxpayer in man hours and crowd courts and prison cells better used for real criminals. Then again, you’ll have to admit your own time is probably better used dealing with real criminals. Probably the most upsetting part of dealing with activists is they’re wasting your time. You’d really rather not be there.
Most people would be deterred by such police actions. However, activists aren’t. This only gives them something else to protest against. They take the immediacy of the situation as a call to action and proceed to come to the aid of someone being arrested.
Since arrests don’t deter this behavior and instead encourage it, you’d be much better off not making arrests and just walking away. This is where discretion comes into play and this is not the time to try to lay down your authority because it will only make the situation worse, for you, for them, for the taxpayer.