About the London riots, how can one argue that it was caused by 'inequality?'
I think that you probably want to make some arguments about how the riots that happened in London were not necessarily the result of one specific police action. Rather, they were reflective of a condition that had grown over time.
Most of the riots happened in neighborhoods that are economically depressed. Certainly, one can accept what the Prime Minister and others are suggesting in that the actions of the rioters were isolated "hoodlums" and isolated "law breakers." Yet, if one were to argue sociological realities of inequality as part of the reason for the riots, the analysis goes deeper than "bad apples:"
Tensions have been bubbling in Britain for some time, with the economy struggling to grow after an 18-month recession, one in five young people out of work and high inflation squeezing incomes and hitting the poor hardest.
The "inequality" argument behind the riots would reside here. The economic problems that have been a part of the world state of affairs has impacted economically challenged neighborhoods more. All people have been challenged by the economic climate of the times, but those who live in areas that were already spread thin are finding more despair. Unemployment seems to be everywhere, but in areas where finding work was already a challenge, this is a condition that is even more pervasive. Add to this that these areas lost vital government funding, and the Prime Minister's opposition's argument that "cuts to police budgets had contributed to the escalation in violence" resonates even louder. The fundamental state of economic inequality helped to create the conditions where violence was not only a reality, but to some extent, inevitable.