Assimilation is the author's term, though I'm sure he'd agree with you. But he is also talking people (many of whom are foreign nationals) actively seeking anarchy and takeover. I believe he is using "assimilation" here much in the same way another journalist would call a 99.1% Latino school population "diverse." The PC verbiage obscures the message.
These self-segregated neighborhoods often Balkinize large areas. Recently the LA Times reported attempts by Latino gangs (cliques?) to ethnically cleanse Compton of blacks by means of violence. Do I care if they choose not to "assimilate" in this instance? Hell yeah!
I've witnessed these acts of arrogance and stupidity closer to home and on a personal level. I had to contact the police on several occasions in the past when a neighbor made it obvious his actions were intended to aggravate or intimidate me into moving. And guess what? I'm still here! HE moved!
Just as blacks ethnically cleansed whites from Detroit, St. Louis, Newark, etc. by intimidation? Hell, Little Italy in Manhattan was once known as "Little Africa" in the late 19th century, until the Eye-Ties chased out the blacks using knives and clubs. Nothing new here, despite what Calipornians think.