Grant, you are so right-everyone has a right to ride a trail on public land as much as anyone else does. The most responsible thing you can do is report those secret trails to the land managers and perhaps volunteer to help decommission the trail. But wait- you seem to enjoy riding those trails, so maybe you don't mind them being there, eh? You've obviously done your fair share of trail work, so you understand how much work goes into building and maintaining trails.
If I'm correct in the previous two sentences, then I assume you want to protect the trails from being decommissioned by land managers, or perhaps in some cases, getting torn up by livestock or motorcycles . Granted, in some areas, land managers turn a blind eye to undocumented trails, but it is a touchy matter and one must be in tune with the local situation. Even where land managers may seem to let undocumented trails exist, I think it is still irresponsible to advertise and flaunt the trails.
Perhaps in your area, no one has a problem with the building or existence of non-system trails, so perhaps my post is irrelevant to you. If that's the case, you are certainly the exception and you can't expect the technique of "Showing anyone and everyone the trail, no matter who they are" to be an effective way to preserve undocumented trails in most areas. If one does not exercise at least some caution in who they show the trails to, then there is a good chance the trail could eventually be closed down. I think if you are sensitive and respectful of the local ethics, then it is much more likely the locals will, "Show you the goods".
Yes , I'm sure there are those that build their own "private" trails and don't want anyone but a few close friends to ride them. Often these bootlegs are poorly designed, so the builders are likely to blame others when their trail ruts up. Best to stay off those trails anyway. But mostly, it's not about being elitist, it's just common sense. If a trail is undocumented, and you want to preserve it, it probably needs to be kept low key and under the radar, and the only way to logically control that is by hiding the entrances and screening the users. If that's not your thing, then be happy riding all the accepted, legal trails and stay away from the others.
Even if the trail builders are elitist, bitchy assholes, you still want to ride their trail and preserve it, don't you? If not, go back and read the second sentence.