There are gangs of any type, depending on the leaders, on the social background and of the reaction by police and criminal justice system. Some of the street groups we have studied, like some chapters of the Latin Kings and Queens, and Ñetas in Spain, Hip-hopers in Colombia, and Hittistes in north Africa, take care of the physical and mental abuse of their members, including those who are in prison, protecting them from the abuse by other members, by other gangs, and mostly by police. There are of course authoritarian leaders and bullying members, but not more than in other social groups. Mutual aid and solidarity is one of the group priorities. You can notice more infos in the website of TRANGANG.