I think you should have used a word other than "policing". Policing doesn't work well because it's negative reinforcement. People resent being told what to do especially if you have no authority to do so. You're not their boss; you're not the FAA; you're not their mother. Perhaps the best you can do is encourage safe practices and set a good example.
That's my military background showing up. We use "policing" for cleaning up trash, checking for lost items, and generally making sure stuff is squared away.
"Encouragement" doesn't work because sometimes the offender has a bit too much "courage."
It's a tough one, because in other small population activities I've participated in (hunting, fishing, cycling, motorcycling, backpacking) it's usually a small few that really make it harder than it should be for the rest.
For example, in MT (nearly) everyone now practices catch and release. Here in PA I've seen
many nice fish laying on the side of the river, left to rot because Clem was "too tired" to carry his catch to the road.
What's the difference?
I think in MT there has been a steady shift after years of fishermen telling each other, "Hey, dude -- don't ruin it for the rest of us." They pick up riverside trash, give the evil eye to someone walking out with a stringer full, and generally approve of the "So I threw that on back.. even though he was a keeper..." story.
You can't tell too many fishermen anything like that in PA without a fight.
So in PA we fish for hatchery-raised slothful fish while MT maintains a healthy naturally regenerating trout population.
Same thing with camping -- 100 backpackers can use a trail in a month, then one slug comes in, burns down half the woods, leaves plastic bags lying all over, and then the landowner says, "That's enough of that!"
Offroading? Same problem. 300 dirt bikes run a trail without a problem. Then Cletus shows up with pipes off, runs up and down the edges of the landowners pond, muddying up the water and killing the fish.
A week later, lots of "No Posted" signs.
Sure, we all love our freedom and we pilots are individuals to the core.
But it's a small, small world we inhabit, and we all pay a price when numbskulls do stupid stuff.
How to fix? I don't know. Better training? A look of disapproval instead of a chuckle when Joe tells us about the barn he buzzed?