The logical consequence of this argument is for San Francisco to secede from the Union and build a wall around the city to stop foreign homeless people from coming in. And blowing up BART too.
Or just let the inevitable earthquake take care of it.
Housing is certainly an ingredient in the soup. So is inequality. And corruption. A culture that is anti-family, consumerist, pro-drug, individualist.
What else? There's so many factors. A lack of cohesive identity. The American attitude of narcissism and the fuck-you mentality. A lack of willingness to call out ghetto behavior as bad. Neutered teachers and schools preaching that all things are equally good and gradually lowering standards. Entire generations of families that basically feed into gangs. A lack of government ability/will to break up gangs. Incessant, unmitigated advertising. Government controlled media serving white-washed bullshit. Liberalism gone off the rails, generally.
It's a mess.