I think a two pronged approach is needed. One is that we who are responsible and who respect the wilderness need to continue to pick up after ourselves and others, both as individuals and as organizations like 4wd clubs and OB, but the other is that we need to be calling, writing, emailing, etc, our government representatives and telling them that we are doing so and lobbying to keep the trails open. Tell them that we do not accept being barred from the activities and places we love because of a few thoughtless jerks, and we are actively working to clean up and conserve natural places.
We need to have a loud clear voice in high places that highlights our hard and continual efforts to counteract the few idiots that are trashing things. It's great to do the cleanups and education, but if no decision makers know about it, it's largely in vain.