Lifted from the comments: 

It goes without saying chappie is an educator. Also needless to say, our educator chappie has form.

Given the self-satisfied ignorance on display – or malign perversity – I’m guessing Dr Kotsko doesn’t live in a neighbourhood rapidly being enlivened with Congolese and Somali borra gangs, whose social skills, and machetes, are so much in the news here.

Of course, it’s much easier to be dismissive of rapidly changing demographics and to disdain expectations of cultural common ground if your own immediate neighbourhood hasn’t yet been enriched by gangs of machete-wielding sociopaths, or by people butchering animal carcasses in the back garden, or newcomers struggling with the concept of electricity, or getting lively in the name of Islam, or just shitting on your doorstep, as happens in some of the more vibrant areas.

And yes, we’ve been here before.