This is the problem of cultures crossing through migration.
This is the problem with political correctness.
This is the problem with everyone aspiring for growth rather than maintaining the status quo.
The only way to keep people relatively happy is to minimize the integration/assimilation of cultures/races through migration, allowing people to speak their minds without being branded as intolerant and to be happy with the way things are.
Unfortunately this is the way of the future until another war breaks out. Resource and food shortages will soon become a real problem, globally. Populations need to be curtailed. Unfortunately this will only happen through global drought or global war as citizens and politicians don't have the guts to call it as it is.
But as for the rioters currently, I say they should be riddled with rubber bullets. If that fails, bring out the live ammo.