Gang stalking is a hate crime/discrimination or vigilantism against whistle-blowers and/or those ACCUSED of wrong doing such as pedophiles--who have paid thier debt to society by seeving out thier sentence. Other examples are innocent mental patients that stand up for themselves against powerful psychiatrists. It is also an extremist groups attempt to supress truths about institutions and businesses.
Stalkers come from all walks of life and all nationalites. They can be full families and communities and also mercinaries and convicts. The Mafia, for example also engages in these adgendas and co-operates with other gangs to these ends. They all have extremist and vindictive adgendas as well and finacial motivations. They build upon the backs of the KKK and Nazis. The stalkers primary attack is to attack the mental state and psyco-social reputation of the victums. Their crimes are ingenious because they are not quite thefts and not quite vandalism. While many of the perpetrators are police and firemen, the crimes they commit are so subtle and bizarre that today's unware honest citizens and crime fighting barnches of goverement that normally would care are confused and even unwittingly support the harrasment and hazing becuase the victum appears to be an enemy of the state. For example some victums are already semi-disenfranchized. And the goal is to full separte them from all support and to drive them to suicide if not outright kill them. The crimes appear to be ordinary decay or mistakes. For example they will tear shower curtian rings or carve holes in the back of shoes--both of which appear to be ordinary but only the victum knows that it wasn't that way the day before or that he did not cause them. The method can be seen in the film Gaslighting (where a man drives his wife insane by altering the briteness of the lighting in thier house.)
Those that would define these claims as mentally ill in and of themselves are seving the cause of the gang stalking if not being stalkers themselves.