I am from SoCal and I will say the same thing.
It's not about the "city" per se. It's about the specific neighborhoods in those cities if not specific streets.
In LA you have orange county which is predominantly fine as are many other areas. But you also have Compton and East LA and even being a native there are pockets in there I wouldn't even drive through - LOL...
I agree. I could drive you around the "inner city" of Detroit and take some of the strangest back roads, but I have driven around that city for decades and know where I am going. However, I would not recommend that you take the same route as I would take. This is similar to any large city in the world.
I worked in downtown Detroit for 10 months on a project and had a great view of the Detroit River from my desk in the City-County Building. I really enjoyed that job and being able to be downtown with great restaurants for lunch and to visit the ethnic festivals in the park across the street and along the riverfront.
And frankly, I have witnessed only one crime in my life, and that was in the parking lot of a large mall north of the city in a well-to-do neighborhood. Some man was trying to car-jack a woman's car, by grabbing her and trying to get her keys, but then ran away when she started yelling.
On the other hand, driving a motorhome in ANY large city in the U.S. is not my favorite thing to do. And it is insanity to try to drive one in San Francisco or LA because traffic is horrible and drivers will not let you change lanes and are overly aggressive.
Also, I do not "break camp" whenever I take my rig out to run an errand. I leave my water hose, sewer hose if a hookup site, chairs, tablecloth on picnic table, etc. Never had anything stolen though I do have a sign that says "Be right back" so people do not think I have abandoned my belongings. I also make a point wherever I am to chat with neighbors so they get to know me and be more likely to watch my things. Most fellow campers keep an eye out on what is happening around them anyway.