Small groups

Suppose we now have those same 1 million people, but instead of living in one big city, they are spread out in small villages of around 100 people each, with the distance between villages around 1 days travel time apart.  Travel time is the focus, rather than distance, because the issue is about the ease of an individual in 'getting to' a collection of people.

Then it is obvious that in 99 of 100 of those villages, there is not one antisocial person, and therefore the inhabitants may never have to cope with one.  In the one in 100 villages which happens to have one, they will be well known, and easy to deal with.  Summary execution seems a good solution. 

Another is banishment, but that depends on whether the neighbouring villages are seen as friends, in which case you probably dont want to export the problem, or enemies, in which case you dont care.  In either case, the problem is easily managed, and does not lead to excessive fear reactions among the whole population.

It should be obvious that the small villages do not need a big bureaucracy in handling the issues involved, one strong-arm man, and a simple justice system, should be plenty to handle these situations.  In fact since the village will have had to deal with this individual since birth, it is highly likely the problem will have been solved well before it gets to the unmanageable stage. Making the travel time between villages large enough makes it difficult for the individual to do a 'raid' on the next village, unlike the large city situation.

Note that I say nothing about other forms of communication.  Obviously it is possible to have full telephone/video/internet etc comms between all the villages, which allows normal commerce and interaction.  It is just helps enormously to limit the actual physical capability to reduce both the perceived and actual problems of antisocial behavior.