There is one thing we can all do (and I would bet that most of us already do this) -- clean up the trash that people have left at our boondocking sites. (We bring Hefty bags just for this purpose.) This is more than just "do-gooder-ism" -- and more than just setting an example. If a site is clean, future campers are more likely to feel inhibited about littering. If it is already trashy, they are more likely to adopt an "anything goes" mentality. So cleaning up the trash not only sends a message, it can also influence behavior. (Obviously, there are people who will litter, no matter what. This is about the folks who are not truly "bad guys.")
This is a variant on the "broken windows" school of policing -- if a neighborhood looks terrible, street criminals feel more at home.
