yob is a slang term for an uncouth or thuggish blue collar person
Confusing as the article said "Yobs Laughed" and then went to to describe the rock throwers as Asians. It was my understanding that "Yobs" is a term to describe aimless, unemployed, drunken white youths (who, in all fairness, are responsible for much of the violent, senseless crime that currently plagues England).