Gangs are no different now than they were in the past, just a little better weaponized and some better organised. There have been notorious gangs of the past among the Irish, Italian, Vietnamese, Chinese, Romanians, Lebanese, Catholics, Protestants etc etc. Polynesian gangs are just the latest manifestation of such activity. Nothing new. 6th century Constantinople had one of the most vicious gangs in the Blues and the Greens. Peaky Blinders is just one English gang on TV based on an historical gang of Birmingham. Gangs have existed throughout history and usually get together as protection against others who threaten them. Sometimes the gangs are within single ethnic groups, such as the Assyrians in the Fairfield area in the 80s and 90s. Many of the members of such gangs will finally drift away and become stable citizens. Many will do goal time. Some will die. Human nature I'm afraid