Surf Gang?
NZfromHK can maybe shed light on this matter?
This probably refers to youth gangs who frequent beaches and go surfing?
But to be serious, Sydney conflicts has deep roots. My take on the matter is that the native Australians are sick and tired of the ways the Lebanese Muslim migrants are behaving. They were harrassing local girls sunbathing in bikinis and even assaulted lifeguards and said "This area is ours!".
A lot of Australians, like middle-to-blue-collar class Britons, may love social welfare, but they have very low BS tolerance as far as PC or defence is concerned. Undedidedly politically incorrect.