In the United States, we have police officers to handle most offenses. While citizens should not stand idly by if they see a serious crime being committed, they should not actively patrol the streets looking for crime. As Phoenix Jones is learning, just because he uses nonlethal pepper spray does not put him on an equal level with police. As the Seattle PD is learning, having a “superhero” patrol downtown is embarrassing to the organization. Increase patrols and replace Phoenix Jones with police to make Seattle a better place.
Vigilante justice makes government meaningless. Insofar as we think that there are specialized institutions for dealing justice, that they should exist and that they are not absolutely corrupt, we should want to defer to them. In taking matters into our own hands, we risk normalizing vigilante behavior, which may cause greater harm in the long run than if it were not. If there is no way to restrain vigilantes, either formally or informally, they will no doubt crop up, and we should not have to be reminded of what kinds of perpetual revenge-seeking this can set off.
Actively seeking out criminals is a poor choice for average citizens. Law enforcement exists "to protect and serve," and then the courts have the responsibility of deciding what is just and unjust. It doesn't matter if you are a Seattle superhero, an Idaho militiaman or a disgruntled postal worker. You do not have the training, experience or the right to judge right from wrong and then act on those judgments. Whatever failings our government and legal system have, they keep us safe while still respecting personal privacy – at least when compared to the average authoritarian regime.