I think it's hard to take one situation and try to generalize about how a given town is, or how "locals" are. Things vary so much place to place, park to park, or local to local, even police officer to another police officer.
I once had police knock on my camper door (not late at night, around 8pm) when I was boondocking in a national forest. They wanted to see my ID. I didn't understand their concern (I was only there for one night, passing through), but as they spoke I got some insight into their concern. Apparently there was another camper just down the road who'd been there for some time. We were not super close to a town, but probably close enough that they felt more comfortable knowing who was out there.
Another time, in Arizona, I was pretty far off into public land on a dirt road, and was awakened in the middle of the night not just by a police car, but by about 4 or 5 police cars and a police helicopter. They stopped to check my ID and ask whether I'd seen anyone out there. They were apparently searching for a fugitive. So, you never know the "backstory" of what police in a given area are dealing with, and like it or not there are criminals heading for the boondocks too.
There are also places that attract drug addicts (like Slab City at the Salton Sea) and those addicts tend to cause problems. Slab City sees a lot of calls to the town's emergency services, both for fire and ambulance. On my last trip to the area I saw an ambulance rush by while I toured Salvation Mountain. Property crime in the small town adjacent to Slab City is higher than average for the US
https://www.bestplaces.net/crime/city/california/niland and property crime tends to be an issue in areas where there are large numbers of addicts, as they often steal to support their drug use. San Francisco is a case in point with skyrocketing crime levels connected with huge numbers of "homeless" street addicts.
There are large urban areas around the nation where you'll find clusters of homeless living in vehicles, and typically you'll find a significant number of addicts in such populations. So, I think some of the prejudice against nomads comes from people who have concerns about these kinds of scenarios, even though nomads are a different group, and are more functional, eg having the ability to travel, which many of the people living in broken down vehicles in urban centers seem not to have.