That lower middle class includes many young couples with children who, if they're fortunate enough to own a starter home, are paying very high taxes for a home located not far from a slum, often with twenty illegal aliens living next door, and the local school is overburdened with kids of illegal aliens. If by chance they must take one of their kids to an emergency room, they should be prepared to wait for the hordes of illegal aliens using the facility to be treated, free.
This scenario is causing much resentment, because these young homeowners/taxpayers/citizens realize that they're the ones paying for the mess. The illegals sure aren't. Illegal aliens are sucking California's social services dry without a peep from the politicians.
It's never been the life cycle of southern California that an ever increasing percentage of population is poor, uneducated and unable to speak the language of the country they were born in. That's not maturity. That's decay.
My parents live in Palm Beach County Florida, where there is NO native born working class. You have affluent, older whites who hire Haitians, Guatemalans and Mexicans to do the drudge work. A similar situation to what you describe here.
Here in New York, the question has become, "where are they (the white working class) going to flee to now? I live in a neighborhood where houses sell for $400,000 and up, but where the rentals are filled with immigrants, legal and illegal. Anyone who wants a starter home in metro NYC for under $350,000 has to either live in the ghetto (and even this is getting more difficult. Or move WAY out to "Outerwhitelandia." You now have NYPD cops who (illegally) commute 75 miles from Eastern Pennsylvania to NYC. I think that's insane, but its their choice.