Vigilantes are indeed people who take it themselves to deal out punishment, for example lynch-mobs, "punishment beatings" in Northern Ireland, and pict's Glaswegian with a baseball bat.

The pillory historically represented a collaboration between official justice and vigilantism/mob violence. The idea wasn't so much humiliation as keeping the person available for the mob to deal with as they wished, by throwing anything the wanted at them. A sort of cross between temporary crucifixion and public stoning. (That's where the Taliban analogy came in) It wasn't uncommon for people in the pillory to be killed. And being put in the pillory was typically accompanied by cropping the ears, or nailing them to the pillory.

Take away the mob violence and so forth, and I hardly think that it would be seen by many young vandals as much of a humiliation In fact more probably the reverse, it'd be more of a reward. Fifteen minutes of fame.