I would say that what is described in this thread is a symptom of mutual cultural conflict between a minority dispossessed people and the dominant culture, a process of conflict that has been going on for hundreds of years. Some of this conflict is briefly described here:
http://en.wikipedia.org/wiki/Roma_society_and_culture
Jews in medieval Europe, native Americans in 19th-century United States, aborigines in modern-day Australia -- these are other dispossessed groups that have similarly been criticized for their "thieving" ways. Of course, incidents occur as a symptom of this conflict that support the stereotype -- especially for those in the dominant culture victimized by these clashes. But why do they occur? And how much do those in the dominant culture realize the injury done to Roma on account of hundreds of years of exclusion, persecution, and dispossession.