"How hard is it to say Hi and casually educate folks nicely about general etiquette if they are so lacking in common-sense without making it sound as though RVers are becoming the most unfriendliest grumpy folks around."
In my experience, what you're suggesting can be taken the wrong way by a lot of people. I don't know that there is a polite and non-insulting way of telling someone they parked too close to you, or your group of campers. Most of the people I know will probably pull an attitude very like: "It's a big desert, public land, and I'll park where I want to".
Just no easy way to tell people to "take a hike". :)