I don't think anyone understands that there are hundreds of vials all over the world - in third world countries in Africa, Europe, Russia, etc, and I think that destroying the small amount of Smallpox we know about versus all of it that was left behind in laboratories and stuff won't make much of a difference.
But, it isn't very necessary to keep it, but I DO believe we should get just-in-case shots of Cowpox to prevent Smallpox.