skyofblue,

1) Their are two native reserves within the confines of Metro-Montreal.  Their shared basic common culture is not Judeo-Christian.  2) People are always identifying this so-called "basic common culture" in a generic fashion, as, once one gets into specifics, it's clear that Canadians share a pretty minor "common culture" beyond what is highlighted in our laws, governmental institutions, and national documents.  And most of these elements would receive shared support from those falling outside the so-called Judeo-Christian consensus.  

"But no one ever heard of ethnically-based gangs with real violence..."  You never heard of the mafia?