That's right. The movement IS taking place well outside the small confines of the 100,000+ Tibetan exile population, held together very shakily by a very thin thread. Once the Dalai Lama passes away (and we do hope this is not soon), another piece is shaved off that already thinning thread , or it snaps altogether.
I have never been of the opinion that we should preserve the lineage and make it grow by publicly critiquing people "on the other side", or launching arguments and debates against the naysayers (the Dalai Lama and non-shugden camp in this case). Like you've pointed out, you're spending an awful lot of time fighting against what is a very small number of people, when that same energy could be spent bringing the blessings, knowledge, education, information and most importantly benefit to the rest of the planet, which far far far outnumber that small Dalai Lama, anti-shugden camp!
Secondly, I just don't think it reflects or bodes well that we are trying to preserve and promote a practice that is based upon compassion and wisdom but our actions don't reflect the practice at all. By speaking badly or fighting back against the other camp, we would show the world that this is what DS people do - they fight, they picket, they demonstrate, they put down the Dalai Lama or other Lamas who are still the sole spiritual guides and root Gurus of thousands of other people. Is this the image we want to project to the world of DS practitioners? For the sake of "righting a wrong" within this small, small insignificant community that you've just pointed out.
Weight the pros and the cons. Sure doesn't look worth it to me to "bet" so much of our time, energy, resources and practice for such a small win. We are definitely much better off forgetting the small petty people and focusing on what really matters - helping people, through Shugden's practice and the practices of our lineage. Isn't this what we are in dharma for? To help people??