The magnitude of wealth disparity is high throughout the country... it is not just the Bay Area. High wealth disparity doesn't justify, nor should it explain violent crime, or any crime for that matter.
Umm... European cities do have high wealth disparity. Checkout an ethnic ghetto the next time you're in Manchester or Paris, for example... there are areas of these cities that get scary AF after dark.
Homelessness is not a crime... but the homeless and drug addicted commit a lot of crimes. And they (particularly the drug addicted) frequently have very little to lose and very severe motivators to rob, mug, etc. As others have said, not policing crime is recipe for disaster, chaos, and tragedy. And it is a human tragedy: for the people who are suffering homelessness, drug addiction; the people within those domains who are victims of violent crime, and for society at large.
A lot of homeless people in CA were not born in CA... and a lot of them didn't hit the street in CA... they migrated to the west coast. Drug addicted homeless people flock to SF and LA because (1) the weather is better than many places in the country, (2) the extremely lax policing, (3) availability of drugs, and (4) the social support system: food, shelter, clothes, money. Indulging depravity is not a solution.
SF needs to double/triple police presence, prosecute crime, and significantly increase drug and mental health services.
I was born in SF, lived there off and on for many years, and have family who still live in the Bay Area... parts of SF are just disgusting now (human feces and trash all over place)... parts of Oakland and Berkeley are no better. Parts of Oakland have so much broken safety glass on the street it's a glass/gravel road.
I used walk around SF late at night as little as 10 years ago; now, there are so many places in SF that I would not walk around in after dark unless I had no other choice. This is coming from a white dude who used to play basketball at playgrounds in South Central LA on saturday nights in the late 90's (because the pick-up basketball was that good).
Until you live somewhere else, you may not understand just how bad and crazy the situation in SF, Oakland, Berkeley, Los Angeles really is. Where I live now, I can leave thousands of dollars of stuff in my car in pain sight and nothing gets stolen... ever. My neighbors' kids leave their bikes on their front lawn overnight and they are still there days later.
I once saw a person break into a Telsa on Piedmont Ave. in Oakland at 2pm on Saturday in front of about 50 people to snatch a backpack. WTF?